October: Heat to Snow

We saw highly variable temperatures across the state this month, with record-breaking heat in the early part of October, and record-breaking cold in the latter part. The preliminary statewide October average temperature was 53.7 degrees, less than 1 degree below our 30-year normal. Temperatures were near normal in eastern Illinois, and between 2 and 6 degrees below normal across western Illinois. Preliminary data suggest October was considerably wetter than normal for the entire state. The statewide average October precipitation total was 5.20 inches, approximately 2 inches above the 30-year normal. The wet deviations were particularly large in the northern and southern reaches of the state.

Data are provisional and may change slightly over time

Temperature Variability

Record-breaking high temperatures persisted from September into early October. Average temperatures during the first four days of October were 10 to 14 degrees above normal in the southeast part of the state, and 3 to 8 degrees above normal for the northwest part (see map below). Maximum temperatures broke 90 degrees and minimum temperatures remained in the 70s for several days in southern Illinois. Stations in Saint Clair and White Counties reached 96 degrees on October 2.  Between October 1 and October 4, 46 daily high maximum temperature records and 73 daily high minimum temperature records were broken across Illinois, according to the NOAA National Centers for Environmental Information (NCEI). Additionally, 9 stations broke their all-time October high maximum temperature records, and 13 stations broke their all-time October high minimum temperature records. In one particularly extreme event, the October 1 nighttime minimum temperature at Kaskaskia Lock and Dam in Randolph County was 72 degrees, 10 degrees above the previous daily record and 2 degrees above the all-time October minimum temperature record at that station.

Seasonable temperatures ensued after the heat was broken toward the end of the first week of October. Temperatures from October 5 to October 27 were near normal in eastern Illinois and between 3 and 6 degrees below normal for western Illinois (see map below). Nearly all the state experienced the first fall frost event in the second week of October. Nighttime minimum temperatures dipped below 32 degrees as far south as Pope County and below 28 degrees in Warren and Jo Daviess Counties.

The heat wave that started the month was matched by a strong burst of cold air to close out the month. Temperatures between October 28 and October 31 were 8 to 16 degrees below normal. Similarly, 48 daily low maximum temperature records and 12 daily low minimum temperature records were broken across Illinois over the last four days of the month. Nighttime minimum temperatures dropped below 30 degrees as far south as Pulaski County. The lowest minimum temperature observed in October was 14 degrees in both Carroll and Lee Counties on Halloween night. Halloween was also the coldest on record for 51 stations across Illinois.

The temperature contrast between the start and end of this month may be best summarized in the graph below, which shows daily maximum and minimum temperatures at Springfield Abraham Lincoln Capital Airport this last month. There was a 57° difference between daily maximum temperatures on October 1st and October 31st in Springfield, both of which broke daily records. In fact, 10 Illinois COOP stations broke their daily high maximum temperature record on October 1st and their daily low maximum temperature record on October 31st.

Precipitation

October precipitation was above normal for virtually all of Illinois. The statewide total precipitation in October was 5.20 inches, approximately 2 inches more than the 30-year normal. Areas of far northern and southern Illinois received over 7 inches of rainfall in October. CoCoRaHS observers in New Lenox in Will County and Riverwoods in Lake County recorded over 12 inches of precipitation in October. Expressed as a percent of the long-term mean, areas of northeastern Illinois received more than 200 percent of mean October precipitation, and a broad swath of southern Illinois received over 150 percent of mean October precipitation (see maps below). Significant rainfall helped improve drought conditions in southern Illinois. The latest U.S. Drought Monitor map – current as of October 29 – shows no drought in Illinois for the first time since early August.

The cool down that came at the end of this month brought a variety of precipitation, including snowfall and some snow accumulation in northern and western Illinois. Total snowfall accumulation over the last week of October ranged from over 8 inches in northwestern Illinois to just over a tenth of an inch as far south as Nokomis in Montgomery County. The highest October snowfall total, 8.5 inches, was in Orangeville in Stephenson County. Although late October is early for the first snowfall in Illinois, it is certainly precedented. The map below shows the date of the earliest recorded snowfall (> 0.1 inch) at COOP stations across the state.

Short- and Long-Term Outlooks

Short-term 8- to 14-day outlooks from the Climate Prediction Center show strongly elevated odds of below normal temperatures persisting into the first couple of weeks of November. Concurrently, probabilities are elevated for below normal precipitation out to 14 days, as drier weather is likely to prevail following the first winter storm of the season in Illinois.

Longer-term outlooks for November also show increased odds of below normal temperatures and increased odds of above below normal precipitation. Winter (December–February) outlooks show greater odds of a wetter than normal winter.

 

September Heat, Flooding, & Drought

This past month was tied for the 4th warmest September for Illinois (state average temperatures back to 1895), and the warmest September since 1933. Precipitation varied tremendously from north to south across the state.

Preliminary data suggest that September was tied for the 4th warmest on record for Illinois. The preliminary average statewide September temperature was 71.3 degrees, which is 4.9 degrees above the long-term average. Monthly temperatures ranged from 2 to 4 degrees warmer than normal in northeast Illinois to over 6 degrees warmer than normal in southwest Illinois. The preliminary average statewide precipitation was 5.34 inches, which is 1.9 inches above the long-term September average. However, the data also show large differences in September precipitation totals across the state, with northern Illinois receiving much more than average precipitation, and southern Illinois receiving much less than average.

Data are provisional and may change slightly over time. 

Precipitation, Flooding, & Drought

September precipitation totals reveal a strong north-to-south gradient. Areas of northern and north-central Illinois received in excess of 12 inches of rainfall in September, while areas of southeast Illinois received less than 0.25 inches over the same time period (see maps below). Expressed as a percent of normal September precipitation, these totals ranged from 300 percent of normal in northern Illinois to less than 5 percent of normal in southeast Illinois. Locally, a station near Stockton (Jo Daviess County) observed 16.62 inches in September (nearly 13 inches more than normal), while the station at Smithland Lock & Dam (Pope County) recorded only 0.02 inches (3.5 inches less than normal).

August 2019 was the first months since September 2018 during which the U.S. Drought Monitor identified drought in the state. In September, dryness in east-central Illinois persisted but did not intensify. The latest U.S. Drought Monitor map (September 24) shows a pocket of moderate drought covering parts of Champaign, Ford, Iroquois, and Vermilion counties (see map below). Concurrently, below normal rainfall and above normal temperatures in the southern part of the state produced dryness in September. The latest U.S. Drought Monitor depicts abnormally dry conditions for most of Illinois south of I-64, and a pocket of moderate drought from Pope and Hardin counties in the southeast to Perry and Franklin counties in south-central Illinois. Conditions in southern Illinois have shown some signals of a flash drought, which is a rapidly intensifying drought event, often provoked by existing precipitation deficit combined with intense heat.

Reports from Illinois Farm Bureau CropWatchers regarding drought in east-central and southern Illinois are mixed. Some report the dryness and heat have helped late-planted crops reach maturity, while at the same time possibly sacrificing yield. The recent National Weather Service 7-day precipitation forecast calls for 1 to 4 inches of rain in the northern half of the state, with 7-day forecasted totals less than 0.5 inches in southern Illinois (see map below).

In contrast to the ongoing drought in southern and east-central Illinois, September was abnormally wet for most of northern and north-central Illinois. Persistent, heavy rains led to flooding impacts in parts of northern Illinois, including the closure of several state parks and significant flooding along the Fox and Des Plaines Rivers, among others. Areas in northern and north-central Illinois received in excess of 12 inches of rainfall in September. In most parts of Peoria, Woodford, Marshall, and Livingston Counties, most of the rainfall totals came in a 24-hour period between September 27 and 28. This event created dangerous flash flooding from Peoria into the southwest Chicago suburbs.

The COOP station in Minonk, Illinois (Woodford County) recorded 9.09 inches of rainfall over that 24-hour period, although that likely fell over a less than 12-hour window. This total approached the 24-hour, 500-year storm total of 9.53 inches and surpassed the 12-hour, 500-year storm total of 8.29 inches. A 500-year storm total refers to a precipitation accumulation over a given time period (e.g., 12, 24, 48 hours, etc.) and has a 0.2 percent chance of occurring in a given year. Impressively, the 9.09-inch total in Minonk broke, and nearly doubled, the all-time 24-hour precipitation total record at that station, which was just over 5 inches (data going back to 1895). Images of flooded fields in Woodford and Marshall Counties suggest this most recent heavy precipitation event may delay harvest.

Temperature

 

The September temperature was much more consistent across the state than precipitation, as the entire state experienced above normal temperatures this month (see maps below). Apart from the last full week in September, most of the state has been under the influence of a large high-pressure system this month, centered to our southeast. This system has allowed warm air to intrude from the south/southwest, generating warmer than normal conditions for this time of the year. In fact, the statewide September average temperature was 71.3 degrees, tying it for the 4th warmest September on record in Illinois (back to 1895). September average temperatures across the state ranged from 65 degrees in Jo Daviess County to 78 degrees in Lawrence County. The lowest minimum temperature reported in Illinois in September was 45 degrees in Jo Daviess County on September 5, and the highest maximum temperature reported in Illinois was 97 degrees in both Alexander and Pope Counties on September 16. Well over 100 local daily climate records were broken in Illinois in September, most of which were high daily minimum temperature records. This is attributed to several very warm nights, including the night of September 22, when the nighttime minimum temperature remained above 70 degrees as far north as Elizabeth (Jo Daviess County) and Freeport (Stephenson County). On the night of September 10, the station in Rock Island reported a nighttime minimum temperature of 77 degrees, besting the previous daily record by 3 degrees.

Short-term temperature forecasts call for continued above average temperatures for the first few days of October and then a regression to cooler, more seasonal conditions. Longer term Climate Forecast System (CFS) forecasts from the National Centers for Environmental Protection show probabilities of a 32-degree freeze in Illinois remain below 30 percent into the third week of October. The map below shows the probability of a daily minimum temperature below 32 degrees between October 14th and October 21st.

October 2019 Outlook

 

Looking into October, the 8 to14-day outlook from the Climate Prediction Center (CPC) shows elevated probabilities of above normal temperatures and elevated probabilities of above normal precipitation across the state.

The CPC monthly outlook for October still shows elevated probabilities for below normal temperatures across the northern half of the state, with equal chances (above normal, normal, below normal precipitation) for all but the very northwest corner of Illinois (see maps below).

 

Unequal August Precipitation Leads to Drought in Illinois

August 2019 will be remembered for remarkable differences in monthly precipitation totals across Illinois, as well as the first appearance of drought in the state since September 2018.

It would be inappropriate to summarize August 2019 precipitation across the state using only one adjective. Preliminary data suggest that August was drier than average across much of the state north of I-72 and south of I-64, while much wetter than average conditions prevailed between the two interstates. The preliminary average statewide precipitation was 4.21 inches, which is 0.61 inches below the long-term August average. The preliminary average statewide August temperature was 72.8 degrees, which is 0.7 degrees below the long-term average.

Data are provisional and may change slightly over time

Precipitation & Drought

July 2019 was the first month since November 2018 that ended with below average statewide precipitation. Dryness in the northwest and east-central parts of the state that began in July persisted in August.

Areas in the south-central part of the state, particularly in the western extent of the St. Louis metro east, have received precipitation totals in August between 5 inches and 8 inches above normal, with a station near Patoka (Marion County) reporting the highest August rainfall total of 14.19 inches. Most areas of the state north of I-72 and south of I-64, in contrast, received below normal rainfall in August, in some cases up to 4 inches below normal. The driest area in August covered parts of Ford, Iroquois, and Vermilion counties in east-central Illinois, where precipitation totals were less than 50 percent of their August normal (see maps below).

 

The continued dry conditions from July to August led the U.S. Drought Monitor to identify moderate drought (D1) in northwest and east-central Illinois in their August 13 map. This was the first time the Drought Monitor identified drought in Illinois since September 2018, which represents the largest number of consecutive, drought-free weeks (48) since the Drought Monitor began 20 years ago. The latest Drought Monitor map, from August 29, shows moderate drought persistence in northwest and east-central Illinois (see figure below).

The combination of late planting, due to flooding, and multi-week drought has stressed crops and farmers across central Illinois. Reports from Illinois Farm Bureau CropWatchers discuss corn dropping ears and beans dropping leaves in parts of Champaign County. The recent National Weather Service precipitation forecast calls for between 0.75 inches and 2 inches over the next 7 days for most of the northern half of the state, with little to no precipitation in southern Illinois.

Temperature

Much of the state experienced near normal to slightly below normal temperatures in August. A strong cold front in the early part of the month and the last week of the month resulted in cooler conditions, with minimum temperatures ranging from the high 40s to high 50s across the state. This was particularly the case for the northwest quadrant of Illinois. However, all of the state experienced August temperatures within 2 degrees of the long-term August mean (see maps below). August average temperatures ranged from 79 degrees in Pulaski County to 68 degrees in Jo Davies County. The lowest minimum temperature reported in Illinois in August was 48 degrees in DeKalb County on August 2nd, and the highest maximum temperature reported in Illinois was 98 degrees in Pulaski County on August 20th.

September 2019 Outlook

Looking into September, the monthly outlook from the Climate Prediction Center (CPC) issued on August 31 shows slightly elevated probabilities of below normal temperatures across the northern half of the state, with equal chances of above normal, normal, and below normal temperatures in the southern half.

September precipitation probabilities slightly favor above normal precipitation in the northwest corner of the state, but are equal (above normal, normal, below normal) for the rest of Illinois (see maps below).

September 2019 Temperature Outlook

September 2019 Precipitation Outlook

July 2019: Prolonged stretch of abnormally wet weather comes to an end, along with notable hot and humid conditions.

July 2019 signaled the end of a persistent and historic stretch of abnormally wet conditions across Illinois, along with several notable periods of significantly above average temperatures.

Preliminary data suggest that July 2019 concluded drier than average, with temperatures above the long-term average. The preliminary average statewide July temperature was 77.3°F, which is 1.9°F above the long-term average. The preliminary average statewide precipitation was 3.23 inches, which is 0.85 inches below the long-term average.

Data are provisional and may change slightly over time

Precipitation

After seven consecutive months of above average statewide precipitation, July 2019 marked the end of the historic wet streak with below average statewide precipitation for the first time since November 2018. Despite the overall below average designation, July precipitation across Illinois was not evenly distributed.

Many in southern and northeastern portions of the state experienced near to above average precipitation totals in July, with a station near Highland (Madison County) reporting the highest monthly rainfall total of 9.02 inches. In contrast, large regions of western and central Illinois saw below average rainfall. In fact, multiple localities near the Quad Cities and along the Mississippi River, as well as smaller regions in east-central Illinois received only 10 to 25% of average monthly precipitation (see maps below).

Dating back to June 1, these same regions have reported precipitation departures of around 2 to 4+ inches below the long-term average. This extended stretch of dry conditions prompted the August 1 map from the U.S Drought Monitor (using data through July 30) to continue to highlight areas of abnormally dry conditions across the western and central portions of the state.

Illinois Precipitation Departures Map
Midwest Regional Climate Center (MRCC), accessed 8/1/2019
Illinois Drought Map
U.S Drought Monitor (UDSM) Illinois, accessed 8/1/2019

Interactive July 2019 Climate Station Precipitation Map

Temperature

Despite an overall seasonable and pleasant ending, the first weeks of July brought several extended periods of heat and humidity to Illinois. Most notable was the heat wave that impacted the region from July 18 through July 21, in which every county in Illinois was under an Excessive Heat Warning at some point during the weekend. Throughout this event, daily maximum station temperatures soared into the 90s, with dew points in the mid- to upper 70s. This resulted in heat indices over 100 for many and approached 110 or higher in some localities. Daily temperature departures of 8 to 10+ degrees above average were common across the northern half of the state (see map below).

Illinois July Heatwave Map

Overnight low temperatures during this event did not bring much, if any, relief from the heat. With a daily minimum temperature of only 80 degrees on July 19, Rockford (Winnebago County) set a new all-time record-high minimum temperature. Records for Rockford extend back to 1905.

Looking at July as a whole, the average station temperatures varied from the mid-70s to the low 80s, and monthly temperature departures of 1 to 4 degrees above the long-term average were common for the northern two-thirds of Illinois (see maps below). The highest temperature reading in the state of 98 degrees occurred at two stations, Flora (Clay County) on July 11, and Palestine (Crawford County) on July 21. The lowest minimum temperature of 51 degrees also occurred at two stations, one near Champaign (Champaign County) on July 23, and at a station near Paxton (Ford County) on July 25.

Illinois July Average Temperatures

Ilinois July Temperatuer Departures

Interactive July 2019 Climate Station Temperature Map

August 2019 Outlook

For the remainder of August, the monthly outlook from the Climate Prediction Center (CPC) issued on July 31 favors probabilities for below average temperatures across Illinois and most of the upper Midwest. The outlook also favors near equal chances for below, near, or above average precipitation.

CPC August 2019 Temperature Outlook
August 2019 Temperature Outlook
CPC August 2019 Precipitation Outlook
August 2019 Precipitation Outlook

June 2019: Stormy and Wet with a Warm Finish

June 2019 will be a month remembered for a continuation of above average precipitation and near to seasonably cool temperatures, despite an unseasonably warm finish.

Preliminary data suggest that June 2019 concluded wetter than average, with temperatures slightly below the long-term average. The preliminary average statewide June temperature was 71.0°F, which is 0.9°F below the long-term average. The preliminary average statewide precipitation was 5.39 inches, which is 1.18 inches above the long-term average.

Data are provisional and may change slightly over time

Precipitation and Flooding

After near historic crests at multiple gages along both the Illinois and Mississippi rivers early in the month, water levels continued to slowly recede for many regions heading into July.  However, above average precipitation in June, combined with calculated soil moisture content remaining in the 90th to 99th percentile across Illinois, leaves the state with an elevated risk of continued flooding over the next month, especially in regions that may be affected by storms or locally heavy rainfall.

Flooding concerns along Lake Michigan were common in June. According to the U.S. Army Corps of Engineers, water levels in the Lake Michigan-Huron system have risen by nearly 5 inches throughout the month. By the end of June, average levels were reported to be 33 inches, or about 2.75 feet above the historical June average.  These levels set a new June record by nearly 2 inches. Water levels of this magnitude haven’t been exceeded since 1986.

Preliminary results show that the June 2019 statewide precipitation total of 5.39 inches was 1.18 inches above the long-term average.  This marks the 8th consecutive month in which no part of Illinois has been listed as in drought or abnormally dry by the U.S. Drought Monitor, and the 7th consecutive month with above average statewide precipitation.

June rainfall in Illinois was not evenly distributed. Several regions in the northern half of the state reported precipitation totals slightly below to near average for the month, with localized regions of above average precipitation. A large majority of the southern half of the state experienced more uniform above average precipitation departures, with numerous localities receiving 200 to 300% of normal (see maps below).

A gage near Cobden (Union County) reported the highest official precipitation total for June, with a reading of 10.73 inches.

Interactive June 2019 Climate Station Precipitation Map

Temperatures

Preliminary results show that June finished with a statewide average temperature of 71.0°F, which is 0.9°F below the long-term average.

The middle of the month was characterized by an extended period of unseasonably cool temperatures, while the start of astronomical summer brought a steady warming trend which allowed temperatures to reach into the upper 80s and 90s for the final days of June.

Temperature departures for the month were near to 1 to 3° below average, with average temperature values ranging from the mid-60s up into the mid-70s (see maps below).

The highest maximum temperature recorded in the state, at two separate stations, was 97°F, once at a station near Bentley (Hancock County) on June 5, and once at a station near Flora (Clay County) on June 30.

The lowest minimum temperature of only 43°F was reported in Danville (Vermilion County) on the morning of June 14.

Interactive June 2019 Climate Station Temperature Map

July 2019 Outlook

As we head into July, the monthly outlook from the Climate Prediction Center (CPC) favors slight probabilities for below average temperatures across most of the state, as well as continued probabilities of wetter than average conditions statewide.

 

 

 

May 2019: Exceptionally Wet and Stormy Across Illinois

May 2019 will be a month remembered for exceptional, record-breaking wet conditions locally, as well as an active, stormy, and at times severe weather pattern across the state.

Preliminary data suggest that May 2019 finished significantly wetter than average, with temperatures marginally below the long-term average. The preliminary average statewide May temperature was 62.5°F, which is 0.2°F below the long-term average. The preliminary average statewide precipitation was 8.43 inches, which is 3.83 inches above the long-term average.

Precipitation

Preliminary statewide average precipitation for May was 8.43 inches, which is 3.83 inches above the long-term average, marking six consecutive months with above average statewide precipitation. As it stands now, spring 2019 will rank within the top four wettest spring seasons in state history (March–May), with May 2019 ranking as the third wettest May in state history.

The multi-sensor precipitation departure map for Illinois shows that practically the entire state received above average precipitation for the month. The only exception was a small region in east-central Illinois near Edgar County, where near to slightly below average precipitation occurred (see maps below).

Portions of west-central and northern Illinois reported the heaviest rainfall for the month, where monthly precipitation departures of 5 to 8 inches above average were common, bringing 200 to 300 percent of average monthly rainfall.  An area roughly defined between Quincy and the Quad Cities extending eastward to near Peoria received the most precipitation in the state, with 7 rain gages in this region recording 13 or more inches of rainfall during May.

A gage near Dallas City (Hancock County) reported the highest precipitation total for May, with an impressive 14.75 inches.

Data from the National Weather Service showed that with a report of 8.25 inches, Chicago experienced its wettest May on record, beating the 8.21-inch reading that was set just last year in May 2018.

The abnormally wet May weather has led to a continuation of elevated flooding risks and significant planting delays for the Illinois agricultural community.  Moderate and major flooding along many local streams and rivers is still ongoing, with flood warnings along both the Illinois and Mississippi Rivers in effect until further notice.

Wet, active, and stormy weather has not only been an issue for Illinois, but also the weather has been a growing risk across much of the central and southern Midwest including the Corn Belt where notable above average precipitation departures for May were also present (see map below).

Severe Weather

In addition to the relentless rainfall, multiple rounds of severe weather impacted the state throughout the month. Statewide, 218 severe weather reports were noted from the Storm Prediction Center, 20 for tornadoes (red), 52 for hail (green), and 146 for wind (blue). Note that multiple reports may be generated for a single event.

Map of May 2019 Severe Weather Reports in Illinois, updated 6/4/2019

Temperature

Preliminary results show that May 2019 finished with a statewide average temperature of 62.5°F, which is 0.2°F below the long-term average.

Monthly temperature departures showed that the northern third of the state generally saw average temperatures of 1 to 3 degrees below normal, while the southern third of the state generally saw average temperatures of 1 to 3 degrees above normal, with near normal temperatures occurring throughout central Illinois.

The highest maximum temperature in the state was recorded at the Kaskaskia River Navigation Lock (Randolph County) with a reading of 93°F on May 26. In contrast, the lowest minimum temperature of 31°F was recorded at the Chicago Botanical Garden (Cook County) on May 4.

June 2019

Although an active weather pattern looks to continue at least for a portion of the first full week of June, the monthly outlook from the Climate Prediction Center favors equal probabilities for below, near, or above average precipitation and temperatures across Illinois for June 2019.

April 2019: An Active Weather Pattern and Late Season Snow!

April 2019 will be a month remembered for a continuation of an active and stormy weather pattern across Illinois, with two short lived, yet notable and uncommon late season snow events which impacted many in northern portions of the state.

The month finished noticeably wetter than average, with temperatures marginally below the long-term average. The preliminary average statewide April temperature was 52.0°F, which is 0.6°F below the long term average. The preliminary average statewide precipitation was 4.58 inches, which is 0.80 inches above the long term average.

Note: Data are provisional and may change slightly over time.

Precipitation

Preliminary statewide average precipitation for April was 4.58 inches, which is 0.80 inches above the long term average.

Precipitation in Illinois has been above average since December 2018. Preliminary data would rank this as the 7th wettest December – April period in state history. The end of April 2019 marked six months since any portion of the state has been classified as in drought, or abnormally dry by the U.S Drought Monitor..

An active spring weather pattern resulted in a majority of regions in northern, eastern, and southern portions of the state receiving over 100% of average monthly precipitation, with localized amounts approaching 200%.  Smaller regions of the state in west-central Illinois – roughly between the Mississippi and Illinois rivers are the only locations to receive near or below average precipitation for the month (see map below).

The heaviest precipitation fell in extreme southern Illinois, especially in counties bordering the Wabash and Mississippi Rivers, where 6 to 8+ inches were common (see map below).  The highest total in the state was reported at a station near Cobden (Union County) with 8.31 inches.

Heading into May, flooding remains an ongoing concern for the state, as soil moisture percentiles remain in the 90th to 95th percent range.

As of April 30th, 134 river gauges affecting Illinois were reported with crests in minor, moderate, or major flood stages. The greatest threat continues to remain along the Mississippi River. River flooding concerns were intensified by several days or heavy rains during the last week of April.

Snowfall

A majority of April snowfall came from two short lived, yet notable late season events that impacted many in northern portions of the state.

The first event on the weekend of April 13th and 14th brought widespread reports of 1 to 5 inches along a corridor extending from near Quincy, and running northeast toward Chicago and the Illinois/Wisconsin border. Several localities west and north of Chicago reported 6 to 8+ inches. Notable accumulations were measured as far south as Peoria. An accumulation of 5.4 inches at Chicago O’Hare Airport tied the record for the snowiest calendar day this late in the season.  April 16, 1961 also recorded 5.4 inches of snow.

The second snow event on April 27th brought a variety of wintry precipitation types to locations in northern Illinois, including another round of accumulating snow for many from Chicago and points north and west.  With 3.7 inches, this was the latest 2+ inch snow event on record for Rockford (Winnebago County).

The maximum monthly snowfall in Illinois was reported at a station near St. Charles (Kane County) with an impressive 13.5 inches.

Temperature

Preliminary results show that April 2019 finished with a statewide average temperature of 52.0°F which is 0.6°F below the long term average.

Despite several significant temperature swings throughout the month, which are common during springtime, statewide April temperatures finished right around the long term average. A few pockets in extreme southern Illinois reported slightly above average, and sporadic regions in northern Illinois reported slightly below the long term average.  This is a welcome change from last year,  April 2018, which ranked as the second coldest April on record.

The highest temperature in the state was recorded at a station near Jerseyville (Jersey County) with a reading of 85°F on April 23.  In contrast, the lowest temperature of 18°F was recorded at a station in Altona (Knox County) on April 1.

May 2019

Looking ahead at the rest of May 2019, the Climate Prediction Center (CPC) is favoring probabilities of above average temperatures for the southeast half of the state, with equal chances of above, near, or below average temperatures for the northwest half of the state. Unfortunately, an active weather pattern looks to persist, as the May outlook favors probabilities of above average precipitation statewide.

Meteorological Winter Recap: 2018-2019

Winter Review:  December – February (2018-2019)

Although the first week of March 2019 does not give us the satisfaction that spring will be arriving in the near future, it does mark the end of the meteorological winter season, which runs from December – February.

Despite what felt like an eternity of below average temperatures, the season as a whole finished with temperatures relatively close to the long term average. Referring to the map below, which represents average temperature departures, a few localities in the west-central and northwest portions of the state saw temperature departures of 1°F or more below average.  On the opposite end, locations in southern Illinois experienced temperature departures of 1-2°F above average during the 2018-19 winter season.

Statewide temperatures averaged 29.9°F, 0.8° above the long term average.

Average temperature for the season ranged from the low 20s north, to around 40° toward extreme southern Illinois.  Large variations occurred with seasonal highs in the 70s and lows in the -30s. The maximum temperature of 71°F occurred on Dec. 1 at Kaskaskia Navigation Lock in Randolph County.  The lowest temperature of -38°F occurred on Jan. 31 at Mt. Carroll in Carroll County, setting a new state record minimum temperature.

The last two days of January brought widespread cold weather to Illinois.  Many locations experienced some of the coldest weather that has been seen in decades allowing numerous daily and station record lows to be broken.  This event produced statewide temperature departures of 20 to 30° below average.

To gain additional perspective on this event, the updated map below displays the minimum temperature recording at stations throughout Illinois with at least 20 years of data.  The color of the station plot represents the month of occurrence, and temperatures in bold represent new records that were set in 2019 (click the map for a larger PDF version).

Precipitation was abundant throughout the state this winter season (see map below), this allowed the entire state to remain free of any abnormally dry, or drought designations during this period. Above average precipitation occurred every month during the season. Generally precipitation totals across Illinois ranged from 5 to nearly 15 inches, with counties south of I-70 experiencing the most precipitation.

Most remarkable was the 21.18 inches of precipitation reported at Smithland Lock and Dam on the lower Ohio River.  Overall, both southern and northwest Illinois received over 150% of their average winter precipitation, with several localities approaching 200% (see map below).

Statewide seasonal precipitation averaged 9.67 inches, which is 2.85 inches above the long-term average, ranking as the 6th wettest winter season on record for the state (with records going back to 1895-96).

The total accumulated snowfall map shows that snowfall occurred statewide this winter, with the heaviest accumulations centered in northwestern Illinois, and counties along the Illinois/Wisconsin border. Totals ranged from 1 to 10 inches in southern Illinois, 10 to 20 inches in central Illinois, and 20 to over 40 inches in northern Illinois.

 

Stormy, wet, and chilly February for Illinois

February 2019 will be a month remembered for an unseasonably active storm pattern, a majority of the month was characterized by a seemingly constant succession of storms resulting in moderate snow accumulations for the northern counties, and persistent rain events and widespread flooding for the far southern counties.  Between storm systems we experienced noticeable temperature swings, and periods of seasonable weather.

Statewide, February ended colder and substantially wetter than the long term average.  The preliminary average statewide February temperature was 28.6°F, which is 2.3°F below the long term average.  The preliminary average statewide precipitation was 3.33 inches, which is 1.27 inches above the long term average.

Data are provisional and may change slightly over time.

Temperature

Preliminary results show that February 2019 finished with a statewide average temperature of 28.6°F which is 2.3°F below the long term average.

The maximum February temperature of 70°F was reported at two stations, Dixon Springs (Pope County) on February 3rd, and Kaskaskia River Lock (Randolph County) on February 4th.  These temperatures came less than a week after the historic Arctic outbreak in late January, which shattered numerous all time station and daily record lows across Illinois.  Over the course of five days many stations across the state saw temperature differences of around 70 degrees or more from Jan. 31 to Feb. 4.

The minimum state temperature was -36°F reported at the Mt. Carroll observation station (Carroll County) on February 1st, a day after the station recorded a potential record state minimum temperature of -38°F on last day of January 2019.

The map below depicts average monthly statewide temperature departures for Illinois.  In February, the departure gradients tended to align in a southwest to northeast fashion, following the larger scale storm tracks.   Overall, Southeastern Illinois saw temperature departures averaging one to three degrees above normal, while much of Central Illinois was near the long term average, and a larger region in the vicinity of Northwest Illinois saw temperature departures averaging two to five degrees below normal.

Precipitation

Preliminary statewide average precipitation for February was 3.33 inches, which is 1.27 inches above the long term average.

Total precipitation was one of the biggest weather concerns for February.  While locations in the center of the state, roughly between I-80 and I-70, received anywhere from 1.5-4.0 inches of precipitation for February, the most impressive totals fell in far Northwestern and Southern Illinois (see map below). In Southern Illinois February totals in excess of 6.0 inches were common, with five stations reporting over 8.0 inches of precipitation for the month.

The highest monthly total was reported at Smithland Lock and Dam (Pope County) with an impressive 10.68 inches.  This ranks as the wettest February on record for the station, with records going back to 1981.

The persistent February precipitation corresponded to monthly totals of 300-400% percent of normal for Northwestern Illinois, and 200-300+% of normal for Southern Illinois (see map below).

Once final numbers are calculated, Feb. 2019 is on track to rank within the top 15 wettest statewide February’s on record.  Abundant regional February rainfall also contributed to a major flooding event in the lower Ohio River.  Both the Smithland Lock and Dam and Cairo river gauges crested at over 10 feet above flood stage during the last week in February. Maximum river stages are expected to be within the top 5 highest on record, according to data compiled by the National Weather Service.

Soil moisture percentiles for the month of February remained in the  90th percentile or higher across Illinois.

Snowfall

Snowfall occurred statewide during February, but was most plentiful in counties along the Illinois/Wisconsin border, where 10+ inches of accumulation were common (see map below)

The highest point snowfall total of 25.7 inches was reported at a station in Galena (Jo Daviess County).

Outlook for March 2019

Looking ahead at the rest of March 2019, the Climate Prediction Center is favoring moderate probabilities of colder than average temperatures statewide.  The highest probabilities are located in the northwestern portion of the state.  Slightly increased probabilities of a wetter than normal March are forecast for extreme southern Illinois, the same regions that have already experienced unseasonably wet conditions for a majority of the winter.

Check back soon for a recap of the 2018-2019 meteorological winter season.

A warm start to January, followed by an abundance of snow and record breaking cold!

January 2019 will be a month remembered by an unseasonably warm start, followed by several cold air outbreaks and a torrent of winter storms that finally made it feel like January in the Midwest. The last two days of the month brought a monumental Arctic air outbreak that shattered many record cold temperatures across the state.

January ended cooler, and substantially wetter than the long term average.  The preliminary average statewide January temperature was 24.7°F, which is -1.7°F below the long term average.  The preliminary average statewide precipitation was 3.51 inches, which is 1.44 inches above the long term average.

Data are provisional and may change slightly over time

Temperature

State Record Cold Temperature in Jeopardy:

A National Oceanic and Atmospheric Administration (NOAA) cooperative (COOP) weather observer at Mt. Carroll (Carroll County) reported a temperature of -38°F  on the morning of January 31st.  This unofficial temperature is currently under review by the State Extremes Committee, and if confirmed with be a new state record.  The current record is -36°F recorded in Congerville (Woodford County) on January 5, 1999.

In addition, multiple all time station record lows were set in Illinois on the morning of January 31st.  Some notable records include, Moline (Rock Island County) with a reading of -33°F , and Rockford (Winnebago County) with a reading of -31°F, as reported by the National Weather Service.

Preliminary results show that January 2019 finished with a statewide average temperature of 24.7°F which is -1.7°F degrees below the long term average.

January temperatures were a roller coaster over the course of the month, as depicted in the plot below, showing high and low temperatures and averages for Champaign-Urbana throughout the month.  Champaign-Urbana was chosen since the State Climate Office is located here, but this trend can be representative of the state as a whole.

Trends in temperatures across the entire state are depicted in the maps below.. The first 10 days of January saw statewide average temperature departures of around +9 to +14 degrees.  On the reverse end, looking at the last 10 days of the month, we experienced average temperature departures of around -5 to -21 degrees in a south to north pattern across the state.  The most extreme departures were in Northwest Illinois.

Temperatures for the month as a whole were closer to the long term average (see map below).  Regions near, and south of I-70 generally reported departures of one to three degrees above the long term average.  However, many locations in Northern Illinois reported departures of one to three degrees below the long term average, while the central portion of the state was near to slightly below average.

  • The highest temperature recorded for the month, was 66°F which occurred at two separate stations, Grand Chain Dam (Pulaski County) on January 2nd, 2019, and Jerseyville (Jersey County) on January 8th, 2019.
  • The lowest temperature recorded for the month was -38°F* at Mount Carroll (Carroll County) on January 31st, 2019 – *this recording is currently under review by the State Extremes Committee.

Precipitation

Preliminary statewide average precipitation for January was 3.51 inches, which is 1.44 inches above the long term average.

An active weather pattern beginning in the middle of the month allowed several large weather systems, and numerous smaller clipper type systems to traverse the state.  These storms were accompanied by heavy rains, accumulating snowfall, and sometimes icy precipitation.  The heaviest precipitation fell in the south/southwestern portion of the state where 5 to 6+ inches were measured (see first map below).  Many regions in Central and Northern Illinois received well over 100% of their average January precipitation, with Northwest Illinois receiving 200 to 300% (see second map below).

  • The highest monthly rainfall total of 6.50 inches occurred at a station near Cobden (Union County), 1.50 inches of which fell in a single day on January 5th, 2019.

Snowfall

Snow was abundant across the state in January, with all of Illinois recording at least some accumulating snowfall.  The highest snowfall totals of 15 to over 20+ inches were common in West-central and Northwest Illinois (see map below).

These same regions generally recorded accumulations on the order of 10 to 15+ inches above the long term average.

  • The highest monthly snowfall total was from Moline (Rock Island County) where 30.2 inches were reported, which is 20.8 inches above the long term average, ranking this as the snowiest January on record for the station.
  • Rockford (Winnebago County) received 24.9 inches, which is 14.7 inches above the long term average for January.
  • Chicago O’Hare reported a trace or more of snowfall for 15 consecutive days, from January 17th through January 31st.

Ice cover on Lake Michigan increased to nearly 35% by the end of the month, according to data from the Great Lakes Environmental Research Laboratory (chart below).

MODIS Imagery of Lake Michigan Ice Cover (Feb 1 2019)

Outlook for February 2019

Looking ahead at the rest of February 2019, the Climate Prediction Center is forecasting an above normal chance for a wetter than average February statewide. The highest probabilities are located toward the eastern side of Illinois.  Below average temperatures are favored for much of Central and Northern Illinois, with no strong signal further south.