The preliminary statewide average January temperature was 22.3 degrees, 4.4 degrees below the 1991-2020 average and tied for the 34th coldest on record going back to 1895. The preliminary statewide average total January precipitation was 1.25 inches, 1.06 inches below the 1991-2020 average and tied for the 32nd driest on record statewide.
Data are provisional and may change slightly over time.
Is this what winter used to be?
All four of Illinois’ distinct seasons are getting warmer thanks to human-caused climate change; however, winter is warming far faster than the other seasons. As a result, we have experienced many more mild winters in recent decades; and this trend made last month’s persistently cold weather seem particularly extreme. Daily temperatures and departures from normal in Quincy show much of the first and third weeks of the month had temperatures that were consistently 5 to 30 degrees below normal (Figure 1).
Figure 1. Daily January average temperature departures in Quincy.
January average temperatures ranged from the high teens in northwest Illinois to the low 30s in southern Illinois, between 2 and 8 degrees below normal. Persistent snowpack in southern Illinois helped depress temperatures farther below normal than in relatively snow-less northern Illinois (Figure 2). The warmest point in the state last month was Du Quoin at 31.7 degrees, and the coldest point in the state was Stockton at 16.9 degrees. The few warm spells in January broke 10 daily high maximum temperature records. The extreme cold in the middle of the month broke 23 daily low maximum temperature records and 15 daily low minimum temperature records, including -20 degrees in Springfield.
Figure 2. Maps of (left) January average temperature and (right) January average temperature departures from normal.
Overall, the preliminary statewide average January temperature was 22.3 degrees, 4.4 degrees below the 1991-2020 average and tied for the 34th coldest on record going back to 1895.
Snowy Southern Illinois
Depending on who you talk to, January 2025 was either a very active winter weather month or quite a boring one. An active storm track setup across the southern half of the state in the first week of January, pushing multiple winter storms through the state, which produced multiple rounds of heavy snow mostly along and south of Interstate 70. The result was a strong gradient of snowfall opposite of what is typical for this time of the year, with more in southern Illinois than northern Illinois.
January total snowfall ranged from over 12 inches in south-central Illinois to less than 1 inch in northwest Illinois. Much of the southern half of the state had 1 to 8 inches more snowfall than normal in January, while northern Illinois racked up a 1-to-8-inch snowfall deficit (Figure 3). Last month was the fifth snowiest January on record in Fairfield with 15.6 inches and the snowiest since 1996. Meanwhile, Moline had only 2.3 inches of snow in January, the lowest amount since 2018 and fourth lowest there since 1989.
Figure 3. Maps of (left) January total snowfall and (right) January snowfall departures from normal
Other than a couple of noteworthy snow and ice events, January was otherwise mostly dry across Illinois. Total January precipitation ranged from just over 5 inches in far southern Illinois to less than a quarter of an inch in far northwest Illinois. Most of northern and central parts of the state were around 1 to 2 inches drier than normal last month and only the southern seven counties were wetter than normal (Figure 4).
Overall, the preliminary statewide average total January precipitation was 1.25 inches, 1.06 inches below the 1991-2020 average and tied for the 32nd driest on record statewide.
Figure 4. Maps show (left) January total precipitation and (right) precipitation departure from normal across Illinois.
Outlooks
The Climate Prediction Center outlooks, reflecting model tendencies and expert assessments, continue to lean into La Niña influence on our late winter and early spring weather across the U.S. Here in Illinois, the expectation is for near normal temperatures and above normal precipitation for both the last winter month of February and the first two months of spring (Figure 5).
Figure 5. Maps show (left) temperature and (right) precipitation outlooks for the month of February and February through April.
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.
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.
The preliminary statewide average October temperature was 56.7 degrees, 1.9 degrees above the 1991–2020 average and tied for the 31st warmest on record going back to 1895. The preliminary statewide total October precipitation was 3.46 inches, 0.20 inches above the 1991–2020 average and the 41st wettest on record.
Data are provisional and may change slightly over time.
Mild October Temperatures with Some Extremes Thrown In
For my money, October is the best weather month of the year. The summer heat mellows out and mixes with the first real shots of chilly air. We had both summer- and winter-like weather last month, but a little more of the former than the latter. As the daily temperature departures from normal in Mt. Vernon show, most October days had above average temperatures, including a few days in the final week of the month that were 15 to 20 degrees above normal (Figure 1).
Figure 1. Daily October average temperature departures in Mt. Vernon.
October average temperatures ranged from the low 50s in northern Illinois to the low 60s in southern Illinois, between 1 and 2 degrees above normal in most places (Figure 2). Most of the state saw high temperatures in the upper 80s or low 90s in early October, including 94 in Quincy and 90 in Hoopeston. The brief taste of winter in the last few days of the month brought widespread low temperatures in the low 20s, including 21 degrees in Mt. Vernon and 23 in Bloomington.
The warm periods last month broke 31 daily high maximum temperature records and an incredible 66 daily high minimum temperature records. Aledo in Mercer County broke its all-time October high temperature records last month with a high temperature of 93 degrees on October 3. The cold end to the month broke 18 daily low maximum temperature records and 37 daily low minimum temperature records.
Figure 2. Maps of (left) October average temperature and (right) October average temperature departures from normal.
Overall, the preliminary statewide average October temperature was 56.7 degrees, 1.9 degrees above the 1991–2020 average and tied for the 31st warmest on record going back to 1895.
Dry Start and Wet End to October
The month-end precipitation totals across the state do not tell the entire story of October precipitation. The first two-thirds of the month were somewhat to very dry across the state, as most places were 1 to 2 inches drier than normal through October 24. More active weather brought multiple rounds of rain–and some snow–to Illinois, raising month-end totals near or above the 30-year normals. As Figure 3 shows, Peoria picked up more rain in the last 7 days of October than in the first 24 days, and the month ended just slightly wetter than normal in Peoria. The dry start to the month was ideal for fall harvest, while the wetter end of the month helped improve dry conditions that prevailed in August and September.
Figure 3. Plot of October daily precipitation accumulation in Peoria (shaded area) versus the normal daily accumulation (black line).
October precipitation ranged from nearly 6 inches in northeast Illinois to less than 2.5 inches in the St. Louis Metro East. Most of the state north of Interstate 70 was 1 to 2 inches wetter than normal, while areas farther south were just slightly drier, up to 2 inches drier than normal (Figure 4).
Figure 4. Maps show (left) October total precipitation and (right) October precipitation departure from average.
Last month wasn’t an extremely wet or extremely dry month anywhere in the state; however, the wetter conditions in the northern half of the state helped reduce drought extent from 23 percent of the state on October 3 to 7 percent on October 31. Small areas of western and southern Illinois remain in moderate drought due to longer-term precipitation deficits. For example, the first 10 months of the year have had the third lowest precipitation total in Quincy with 20.17 inches, around 10 inches below average. While topsoil moisture in western Illinois has improved from the wetter end of October, deeper layer moisture and water table levels remain less than ideal because of the long-term dryness.
Overall, the preliminary statewide total October precipitation was 3.46 inches, 0.20 inches above the 1991–2020 average and the 41st wettest on record.
A Spooky, Winter-y Halloween
Like all the horror film characters who inevitably run back into the haunted house, mild October temperatures lulled all of us into a false sense of security. The intense cold, wind, and for some folks, snow on Halloween was more shocking than the sound of a revving chainsaw. Halloween nighttime temperatures dipped into the low 20s and high teens across much of the state, including 18-degree lows in Monmouth and Rochelle (Figure 5). The daytime high temperatures on Halloween were the coldest on record in several spots across the state, including at Chicago’s Midway airport (37 degrees) and Mt. Vernon (43 degrees). The low temperatures on Halloween night also set records in many places, including in Kankakee (24 degrees) and Olney (22 degrees). In fact, this year was the coldest Halloween in Olney since observations began there in 1896.
Halloween snow in northern and central Illinois is not necessarily a rarity but happens once every 4 to 6 years. Measurable snow, with totals exceeding 0.1 inches, was recorded in much of the state north of Interstate 74, with totals as high as 1.5 inches in Mundelein and 0.9 inches at O’Hare (Figure 5). For reference, the average first measurable snow comes in the third or fourth week of November for most of northern and central Illinois, so this year’s event came about two to three weeks early. It’s important to note that an early snowfall does not mean we will necessarily have a very snowy winter… but this State Climatologist can hope.
Figure 5. Maps of (left) nighttime low temperatures and (right) total snowfall on Halloween. Maps are from the Lincoln National Weather Service Office: https://www.weather.gov/ilx/illinois-daily.
Outlooks
November doesn’t get the love it deserves, because it is so often associated with cloudy, blustery weather. But November typically gives us a great mix of pleasant and not-so-pleasant weather and portends the beautiful winter season in Illinois. The latest Climate Prediction Center outlooks lean into El Niño with higher chances of below normal November precipitation. November temperature outlooks are more mixed, with equal chances of warmer and colder weather this month (Figure 6).
Figure 6. Maps of (left) temperature and (right) precipitation outlooks for November.
Meanwhile, NOAA leans even more heavily into El Niño for climatological winter (December–February) outlooks (Figure 7). The outlooks show highest chances of above normal temperatures in winter, with mostly equal chances of above or below normal precipitation.
Figure 7. Maps of (left) temperature and (right) precipitation outlooks for winter (December–February).
October was much cooler and slightly drier than average across Illinois. The preliminary statewide average October temperature was 51.8 degrees, 2.6 degrees below the 30-year normal, and tied for the 19th coolest on record. Preliminary statewide average total precipitation for August was 3.03 inches, 0.21 inches less than the 30-year normal, and the 54th wettest on record.
Data are provisional and may change slightly over time
October Temperatures
Cool weather persisted from the end of September to the first week of October across the state. As the plot below of daily temperature departures from normal in Moline shows, the second week of October was 5 to 10 degrees warmer than average across the state. However, this was followed by a predominantly cooler than average second half of the month.
Eleven daily high maximum temperature records and eight daily high minimum temperature records were broken last month. Concurrently, 66 daily low maximum temperature records and 19 daily low minimum temperature records fell in October. The cool, cloudy day of October 27 broke the month’s low maximum temperature records at seven locations in Illinois. This included the 34-degree high in Kewanee in Henry County, which broke the previous October low maximum temperature record of 36 degrees, set just last year on Halloween.
The maps below show October average temperatures and their departure from the long-term average. October average temperatures ranged from the high 40s in northwest Illinois to the high 50s in southern Illinois, between 2 and 5 degrees below average. The preliminary statewide average October temperature was 51.8 degrees, 2.6 degrees below the 30-year normal and tied for the 19th coolest on record. This follows the cooler than normal months of August and September statewide.
Harvest Fires
The combination of high temperatures, very low humidity, and strong winds created a significant fire risk during the second week of October. The plot below shows a daily mean surface vapor pressure deficit, a measure of atmospheric humidity, at Springfield between January 1 and October 18 of this year (red line) compared to all previous years (gray shaded area). A vapor pressure deficit has been linked to wildfire risk, with higher vapor pressure deficit values indicating a higher risk of wildfire outbreak.
The very high values of vapor pressure deficit in Springfield, near record values on October 14, indicated a warm, dry atmosphere. Existing drought and crops drying down in fields provided ample, dry fuel for wildfire potential. Indeed, several small- to medium-sized field fires broke out across central and south-central Illinois during the second week of October.
First Snow of the Season
The map below shows the climatological earliest first measurable snowfall on record at stations across the state. The dates range from early to mid-October in northern Illinois to mid-November in southern Illinois.
The map below shows the climatological earliest first measurable snowfall on record at stations across the state. The dates range from early to mid-October in northern Illinois to mid-November in southern Illinois.
A Wet End to the Month in Southern Illinois
The first half of October was very dry for the southern half of the state, continuing a very dry September. However, around the middle of the month the atmosphere moved into a pattern more conducive to bringing precipitation into southern Illinois. Areas that received less than a tenth of an inch of rainfall in previous weeks saw widespread 4- to 9-inch precipitation totals during the final two weeks of October.
Belleville, for example, recorded its third wettest October with a total of 7.38 inches, following its wettest August and its second wettest July on record. At the end of October, Belleville was only 4 inches away from its wettest year on record, which was 2008 with 56.83 inches of rain.
Drought Continues in Central Illinois
In contrast to the wet end of October in southern Illinois, much of central Illinois ended yet another month with below average precipitation. The maps below show 30- and 180-day precipitation deficits across the state. Most of central and western Illinois received between 1 and 3 inches below average precipitation in October, adding to existing precipitation deficits from dry months in August and September.
Total six-month precipitation deficits in central Illinois exceed 7 inches in Fulton and Mason Counties and 8 inches in parts of Logan and Macon Counties. At Mount Pulaski in Logan County, for example, the June 1 to November 1 precipitation deficit of 8.47 inches is the third largest on record, smaller only than 1988 and 1893. However, it should be noted that Mount Pulaski and the surrounding areas of Logan and Macon Counties received more precipitation in the first four months of this year than in all of 1988. Therefore, drought conditions, although severe, are not nearly to the extent of those in 1988.
The most recent, October 27th version of the U.S. Drought Monitor showed continued widespread moderate drought across central Illinois in response to the rainfall deficits and below normal soil moisture and streamflow.
Outlooks
Pleasant weather is in store for the state during the first week of November. However, the Climate Prediction Center’s 8- to 14-day outlooks indicate an imminent pattern change in the second week of November, with odds moving back to below average temperatures, especially to the northwest, and above average precipitation statewide.
The most recent one-month outlooks for the entire month of November continue to show a strong La Niña influence, with elevated odds of warmer than normal conditions throughout the central U.S. and drier than normal weather in the south.
Finally, the three-month outlooks for climatological winter, December–February, show equal chances of warmer or colder than normal conditions in Illinois. However, the odds increase for wetter than normal conditions later in winter.
