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.

 

2018 Illinois Climate Recap

 A Climatologic Review: 2018

Now that 2019 is well underway, lets take a moment to reflect back on the climate averages and departures from 2018.

Note:  Data are provisional and may change slightly over time

Temperatures

2018 was a year marked with several climatologically dramatic temperature swings.  The chart below shows monthly temperature departures from the 1980 – 2010 long term average for Illinois.  The most noteworthy feature is the -7.8°F departure that occurred in April, ranking April 2018 as the second coldest April on record for the state (records extend back to 1895).  And with the turn of a calendar page, May saw a +8.0°F departure from the long term mean, ranking May 2018 as the warmest May in state history.

The plot below shows the average statewide temperature (F) by month for 2018, the colors represent meteorological seasons.

The map below shows spatially average temperature departures for the year 2018.   Despite several dramatic temperature swings throughout the seasons, the year as whole finished right around the long term mean statewide.  A few regions in the northwest were a degree below, and a few regions in the south/southeast were a degree above the long term mean.

The statewide average temperature for 2018 was 52.5°F which is 0.2°F  above the long term average.

  • The highest temperature recorded in the state: MORRIS 1 NW in Grundy County with 100°F on May 28th, 2018
  • The lowest temperature recorded in the state:  MORRISON in Whiteside County with -24°F on January 1st, 2018
  • The warmest mean temperature: LAWRENCEVILLE 2WSW in Lawrence County with 59.3°F
  • The coldest mean temperature: PALESTINE in Crawford County with 43.1°F

Precipitation

The chart below shows monthly precipitation departures from the 1980 – 2010 long term average for Illinois in inches.  February saw the wettest departure from average at 2.82 inches.  April saw the driest departure from average at -1.36 inches,

The plot below shows the average statewide precipitation (in) by month for 2018, the colors represent meteorological seasons.

The map below shows precipitation as a percent of normal for the year 2018 in inches.  It was a rather wet year statewide, the highest percentages above average were reported in numerous regions across the extreme northern and southern portions of Illinois, where 125 to 150 percent of normal precipitation was measured.

The statewide estimated average precipitation for 2018 stands at 45.75 inches which is an impressive 5.79  inches above the long term average.

  • The highest yearly precipitation in the state: NASHVILLE 1E in Washington County, with 66.79 inches
  • Largest one day maximum event: CISNE 2.5 in Wayne County with 8.54 inches on September 8th, 2018
  • Snowiest location in the state: BULL VALLEY 2.5 WNW with 55.4 inches, the one day maximum snowfall for the site was 13.1 inches on November 26, 2018

Severe Weather

Severe weather reports for Illinois in 2018 from the NOAA Storm Prediction Center. Note: It is possible to generate multiple report for the same storm/event

Month Total Reports Tornado Hail Wind
January 2 0 2 0
February 1 0 0 1
March 0 0 0 0
April 20 9 4 7
May 170 6 48 116
June 184 11 15 158
July 54 0 6 48
August 40 2 7 31
September 40 2 1 37
October 3 0 0 3
November 0 0 0 0
December 52 34 11 7
Total 566 64 94 408

Illinois Climate Minute: 2018 Recap


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Warm and Stormy December for Illinois

In contrast to November, December 2018 finished warmer than the long term average, was lacking in major winter storms, and brought a historic late season severe weather outbreak.

  • The statewide average temperature for December was 34°F, which is 4.1°F above the long term average.
  • The statewide average precipitation for December was 3.35 inches, which is 0.66 inches above the long term average.
  • The highest temperature recorded for the month was 71°F on December 2nd at the Kaskaskia River Lock and Dam in Randolph County.
  • The lowest temperature recorded for the month was 6°F on December 28th at both the Altona and Mount Carroll stations in Knox and Carroll Counties.
  • The highest monthly rainfall total of 6.83 inches occurred at a station near Chester, which is located in Randolph County.
  • The highest monthly snowfall total was only 3.1 inches, and was recorded at a station near Patoka in Marion County.
  • The National Weather Service confirmed 29 tornadoes in Illinois during the historic December 1st severe weather outbreak.

Data are provisional and may change slightly over time

Temperatures

December favored above average temperatures for the entire Midwest, including Illinois  The map below shows that the largest temperature departures were felt in the upper Midwest, and extending down into much of northern Illinois where several locations finished the month 6 to 7 degrees above the long term average.  Overall, the statewide average temperature for December was 34°F which is 4.1°F above average.

Precipitation

Statewide precipitation totals for December were at or above the long term average. Two storm systems impacting the state during the last week of December helped to bring the monthly totals above normal for much of central and northern Illinois, where precipitation was lacking in the middle of the month.  The highest widespread precipitation totals occurred around and south of I-70.  The maps below show total December precipitation, as well precipitation departures for Illinois.

December was not an ideal month for snow lovers as warmer temperatures, and a combination of environmental factors kept December snow accumulation to a minimum.  The highest accumulations were in the northeast, and in central/west central portions of the state –  where a quick moving cold front brought a majority of the snow accumulation during the first week of December. Total snow accumulations are shown in the map below.

Severe Weather

The National Weather Service confirmed 29 tornadoes across Illinois during the December 1st tornado outbreak, ranking this as the largest December outbreak in state history.  The previous three largest outbreaks are listed below:

  • December 18-19, 1957 with 21 tornadoes
  • December 23, 2015 with 6 tornadoes
  • December 4, 1973 with 5 tornadoes

Most notable was the Taylorsville Tornado in Christian County.  This tornado had a path width over 1/2 mile wide, and estimated wind speeds of 155 mph, ranking it as an EF-3 on the Enhanced Fujita Scale, The Taylorsville tornado caused major damage to 100 homes, and 22 reported injuries.

The map below, from the Storm Prediction Center, pinpoints locations of all severe weather reports from 12/1/2018.  It is evident that the worst of the severe weather, and tornadoes, were confined to west central Illinois.

SPC Storm Reports

In total, 52 severe weather reports were recorded for Illinois this December; 34 reports for tornadoes, 11 for severe hail, and 7 for severe wind.  Note:  It is possible for multiple reports to be created for the same event/storm.

Check out the Twitter link from Kevin Lightly, capturing aerial images of damage in Taylorsville the day after the tornado outbreak:

Outlook for January

Looking ahead at the rest of January 2019, the Climate Prediction Center is forecasting an above normal chance for a drier than average January for a majority of the state. The highest probabilities are centered over northern Illinois and the Great Lakes.  Focusing on temperatures, the highest probabilities for above average temperatures are concentrated over the upper Midwest and North Dakota, with a smaller probability extending into northwest Illinois.

January 2019: CPC One Month Precipitation Outlook
January 2019: CPC One Month Temperature Outlook

Be sure to check back in the coming week for the ‘Illinois 2018 Climate and Weather Recap’ blog entry.