Category: Flooding

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2024 Weather Was Very Warm and Wild

Illinois was both warmer and wetter than the 1991–2020 normal in 2024. The statewide average annual temperature was 55.5 degrees, 2.9 degrees above normal and 2nd warmest on record statewide. Statewide average total precipitation in 2024 was 40.69 inches, 0.05 inches above normal and the 43rd wettest year on record.

The Second Warmest Year on Record

The past year was very warm in Illinois, but the largest temperature departures from normal were outside of the climatologically warmest time of the year. February, March, and November were all at least 4 degrees warmer than normal, while July and August were near to slightly cooler than normal statewide (Figure 1).  

Figure 1. Plot shows 2023 statewide monthly average temperature (black line) and temperature departures from the 1991–2020 normal (red and blue bars).

Average temperatures in Illinois last year ranged from the low 50s in northern Illinois to the low 60s in southern Illinois, between 1 and 6 degrees above normal (Figure 2). The year 2024 was the warmest year on record in Chicago, Peoria, St. Louis, and Paducah, and it was a top 5 warmest year on record in the Quad Cities, Champaign-Urbana, Quincy, and Carbondale, among other places. The warmest point in the state last year was Dixon Springs in Pope County with an average temperature of 60.2 degrees. The coolest point in the state was Stockton in Jo Daviess County with an average temperature of 50.2 degrees.

Figure 2. Maps show 2024 annual average temperature (left) and average temperature departures from the 1991–2020 normal (right).

Last year was the warmest on record in Chicago, which stretches back to the 1870s. The weather station of record for the city of Chicago is currently at O’Hare airport; however, the station’s location has changed multiple times since the 1870s. For the first half of the record, the station was much closer to Lake Michigan, including in the Roanoke Building between 1873 and 1887 and Rosenwald Hall at the University of Chicago between 1926 and 1942. The Chicago National Weather Service office has a complete weather history for Chicago and Rockford: https://www.weather.gov/lot/observation_history.

Despite the likely moderating effect of the lake on temperatures in the early part of Chicago’s record, 2024 was still the warmest year since Ulysses Grant was president. Figure 3 shows the record of annual average temperature in Chicago, illustrating a long-term warming trend the city has experienced over the past 150 years.

Figure 3. Plot shows the annual average temperature in Chicago from 1873 to 2024.

Table 1 shows the number of daily weather records broken at Illinois Cooperative Observer stations in each month of 2024.

Our very mild February led with the highest number of daily high maximum temperature records, with 222 statewide. Meanwhile, the final three months of the year led with the most high minimum temperature records with 101, 67, and 64, respectively. The fleeting but intense cold air outbreak in mid-January in 2024 broke 73 low maximum temperature records and 28 low minimum temperature records. Multiple months had at least 100 daily high precipitation records broken last month, including January, April, July, and November.

Table 1. Table shows the number of daily local weather records in 2023 by month and variable.

2024 Precipitation

Calendar year 2024 had quite variable precipitation, with five months of wetter than normal conditions (January, April, July, November, December) and seven months that were drier than normal (Figure 4).

Figure 4. 2024 monthly total precipitation as a departure from the 1991–2020 normal.

Illinois experienced the 2nd driest February on record statewide, with only 0.48 inches of statewide average February precipitation, about 1.5 inches below normal. A wetter than normal April and May helped refill soils ahead of the growing season, but also delayed crop planting and critical fieldwork in many parts of the state.

July brought multiple rounds of heavy rain to the state, including events that caused widespread damaging flooding in the St. Louis Metro East area: https://storymaps.arcgis.com/stories/df7ac819701a445399d7fe87328b4f77, and the Rockford area: https://www.weather.gov/lot/2024_07_13-14_Flooding. Nashville, Illinois experienced over 6 inches of rain in less than 8 hours on July 16th, forcing overflow of a local reservoir and flooding of several homes.  

For the third consecutive year Illinois fell back into drought in the fall as the months of September and October were 1 to 3 inches drier than normal across the state. Total precipitation in September and October statewide was only 3.48 inches, about 60% of normal and the 12th driest 2-month period on record. Once again, the region’s largest rivers approached low stage, including along the Illinois, Mississippi, and Ohio Rivers, causing some moderate challenges to shipping. November and December were both wetter than normal to end the year.

Figure 5 shows the spatial variability of 2024 precipitation in more detail. Total precipitation last year ranged from over 60 inches in far southern Illinois and the St. Louis Metro East area to less than 35 inches in parts of northern and north-central Illinois. Areas along the Wisconsin and Iowa borders were 2 to 6 inches wetter than normal last year, and areas around St. Louis and along the Interstate 70 corridor were 6 to 12 inches wetter than normal.

Figure 5. Maps show (left) total precipitation and (right) precipitation departures in 2024.

A CoCoRaHS citizen science observer in Metropolis in Massac County had 62.92 inches of precipitation in 2024, making the birth of Superman the wettest point in the state. Meanwhile, another CoCoRaHS observer in El Paso in Woodford County had only 28.22 inches of precipitation in 2024.

Overall, statewide average total precipitation in 2024 was 40.69 inches, 0.05 inches above normal and the 43rd wettest year on record.

2024 Severe Weather

Severe weather came early and often in 2024, with all of our 102 counties affected by strong wind, hail, tornadoes, or heavy rain (Figure 6). Overall, the NOAA Storm Prediction Center reported a preliminary 142 tornadoes in Illinois in 2024, which  would set a new annual tornado record, breaking the 124 event record in 2006, and follows the very active tornado year of 2023 with 121 tornadoes. Figure 6 shows the monthly frequency of tornadoes in 2024 compared to the 1994-2023 average frequency. February through May had above average tornado frequency, and then came a record-breaking July. The 7th month of the year ended with 45 tornadoes in the state, including a massive tornado outbreak in the Chicagoland area on July 15th. In total, the derecho on that evening brought 32 confirmed tornadoes, including several that made it into the Chicago city limits: https://www.weather.gov/lot/2024_07_15_Derecho.  

Only one tornado was reported in the last four months of the year. It is likely the 2024 tornado total will be adjusted, but irrespective of changes, 2024 was an extremely active tornado year and very likely the most active tornado year on record in Illinois

Figure 6. Plot shows tornado frequency by month in 2024 (blue bars) compared to the 1994-2023 average (red bars).

The NOAA Storm Prediction Center also had 216 severe hail reports and 716 severe wind reports in Illinois in 2024. Many of the wind reports came from a strong derecho that moved through the state on June 29. Over one-third of all severe wind reports came on July 15th, including 100+ mph wind reports in Marshall County and Ogle County.

2024 Snowfall

Snow was hard to come by in 2024. Figure 7 shows snowfall departures from normal between January and May, September and December, and for the 2024 year as a whole. Most places in the state had between 5 and 20 inches below normal snowfall last year. Overall, the statewide average total snowfall was just under 12 inches in 2024, below the long term average of 19 inches (Figure 7).

Figure 7. Maps of snowfall departures from normal across Illinois and a plot of statewide average total snowfall in Illinois between 1904 and 2024. The maps show departures from (left) January through May, (middle) September through December, and (right) the entire year of 2024.
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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).

 

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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.

 

 

 

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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.