Overview
A cold and dry January for Illinois.
Temperatures averaged 24.3° for the month, 2.3° lower than the 1991-2020 normal (Figure 1). January 2026 was the 47th coldest January on record.
Precipitation statewide in January was 1.07 inches, 1.24 inches below the 1991-2020 average (Figure 1). The month was the 22nd driest January on record.
Mean provisional streamflow data was sufficiently limited, due to winter conditions, to preclude estimating an aggregate mean streamflow condition statewide for January. Available data suggested that monthly streamflow conditions ranged from much below normal in southern Illinois and central to east-central Illinois, to normal in northern Illinois.
Water surface levels at the end of January were below the full pool or target level at 14 of 19 reporting reservoirs. At the end of January, Lake Shelbyville was 0.1 foot above the winter target level, Carlyle Lake level was 0.3 feet above the winter target level, and Rend Lake was 1.1 feet below the spillway level.
Lake Michigan’s mean level was below its long-term mean for the month.
Shallow groundwater levels were 3.68 feet below the long-term average at the end of January (Figure 1). Levels averaged 0.31 feet below December and 3.03 feet below last year.
Weather/Climate Information (Trent Ford)
January in Illinois was much cooler and drier than normal.
Temperatures averaged 24.3°F, 2.3° below the 1991-2020 normal for January (Table 1, Figure 2). Last month was the 47th coldest January on record statewide.
Of all the crazy weather months in Illinois, January has the largest average day to day temperature variability, and those wild swings were on full display last month. Daily average temperatures in first half of the month were 5 to 25 degrees warmer than normal, and days in the second half of the month were 5 to 25 degrees colder than normal across the state.
January average temperatures ranged from the high teens in northwest Illinois to the mid-30s in far southern Illinois, between 1 and 3 degrees below normal (Figure 2). Snowpack in the southern part of the state during the latter half of January kept both daytime and nighttime temperatures well below average, compared to relatively snow-less northern Illinois.
Precipitation statewide in January was 1.07 inches, 1.24 inches below the 1991-2020 average (Table 1). Plenty of cold air was present when the winter storms moved through our state in the latter half of January, and while this was helpful to produce some impressive snowfall totals, it also limited the liquid water content of the snow. Consequentially, parts of southern Illinois that had 300% or more normal snowfall were also 1 to 2 inches drier than normal last month. In fact, most of the state outside of a narrow band from Peoria to Chicago was 1 to 3 inches drier than normal last month (Figure 3). Only a few places saw more than 3 inches of total January precipitation, while some parts of northwest Illinois had less than an inch for the entire month.
Snow: Last month was a good example of why snowy and wet are two different descriptions of winter weather. Multiple strong winter storms moved through the mid-south in the latter half of January, bringing a lot of snow to the southern half of Illinois. Five counties had locations that approached or exceeded their 1-day snowfall records on January 19th, including over 13 inches in Jackson County. Although the heavy snow was disruptive to travel, it was much preferred over the devastating ice accumulation farther south in places like Nashville.
Overall, January total snowfall ranged from less than 3 inches in northwest Illinois to some isolated pockets of 20 inches in southern Illinois. The northern half of the state only had 10 to 75% of normal January snowfall, while much of southern Illinois had 200 to 500% of normal snowfall last month.
Drought: Illinois is still dealing with an intense drought that began in 2025. The period between August 2025 and January 2026 was top 10 driest on record in most of central Illinois. Bloomington-Normal only received 7.10 inches of precipitation between August 1st and January 31st, which was the 5th driest of any 6-month period on record there and the driest 6 months since 1980. The water table at the Illinois Climate Network station in Peoria as of February 1st was 8 feet deeper than normally this time of the year and is the deepest it has been since measurements began in the mid-2000s. Accordingly, the most recent US Drought Monitor released on January 29th still showed over 60% of the state was still in moderate drought, and much of east-central Illinois remained in extreme drought. Champaign County has been in extreme drought for 14 consecutive weeks ending on January 29th, marking the longest such period since the Drought Monitor began in 2000. Although we typically don’t expect a lot of precipitation in February, wetter weather this month would be very welcome to start improving long-standing drought in the state.
Illinois Climate Network (ICN) (Jennie Atkins)
The Illinois Climate Network (ICN) consists of 20 stations across the state which collects hourly weather and soil information.
Winds were higher again in January with a network average of 8.4 mph, 0.5 mph higher than December and 0.1 mph above the long-term average. ICN Bondville (Champaign County) had the windiest month with the highest average, 8.4 mph, and wind gust, 59.4 mph on January 8.
There was a large variation in temperature in January with an 86° difference between the month’s maximum and minimum. Station highs were in the 50s and 60s while lows fell into the negatives at most stations. Only two stations – ICN Carbondale (Jackson County) and ICN Dixon Springs (Pope County) – had lows above 0°.
Temperatures averaged 24.7° for the month, 6.3° lower than December and -2.9° below the long-term average. The highest temperature was 69.0°, recorded at ICN Carbondale on January 8. The lowest was -17.0°, measured January 23 at ICN Freeport (Stephenson County).
Soil temperatures were 3 to 4° lower with average in the mid-30s with frozen soils at all depths.
Under bare soil, temperatures ranged from 6.9 to 59.8° at 2 inches and 13.6 to 57.2° at 4 inches. Temperatures under sod ranged from 19.7 to 58.9° at 4 inches and 27.0 to 52.5° at 8 inches.
January was another month for the network as all stations reported precipitation totals less than their long-term averages. 10 stations had monthly totals less than an inch. The highest totals were in the south where ICN Dixon Springs (Pope County) recorded 2.70 inches, the month’s largest. Overall, the network averaged 1.19 inches, 0.42 inches less than December and 1.14 inches below the long-term average.
Soil moisture will return to the IWCS in Spring 2026.
Surface Water Information (Bill Saylor)
Provisional monthly mean flows. Due to winter conditions in January, streamflow data was not available for extended periods at several gaging stations. Sufficient data was not available to present Table 2 or to estimate an aggregate mean streamflow condition statewide for January. Available data suggested that monthly streamflow conditions ranged from much below normal in southern Illinois and central to east-central Illinois, to normal in northern Illinois.
Water-Supply Lakes and Major Reservoirs. Table 3 lists selected reservoirs in Illinois, their normal pool or target water surface elevation, and data related to observed variations in water surface elevations. Reservoir levels are obtained from a network of cooperating reservoir operators who report water levels each month. Current reservoir levels reported in Table 3 are representative of the end of the reported month and are presented as the difference in feet from seasonal target level or from full pool, as applies. Years of record represent the number of past reports for the same month used to calculate the average of the month-end values presented in Table 3. For some reservoirs, this average does not include additional period of record prior to a substantial change in reservoir operation. Most reservoirs in Table 3 serve as public water supplies, with the exceptions noted in the last column.
Compared to end-of-December water levels at 19 reservoirs for which levels were reported last month and this month, reported end-of-January water levels were lower at 12 reservoirs, higher at 6 reservoirs, and about the same as at the end of December at 1 reservoir. For the 19 reservoirs with measurements reported for the end of January, water levels were below normal target pool or spillway level at 14 reservoirs, above normal target pool or spillway level at 3 reservoirs, and at about the target level or spillway level at 2 reservoirs.
Major Reservoirs. Compared to water levels at the end of December, at the end of January the water level at Lake Shelbyville was 1.3 feet lower, Carlyle Lake was -0.8 feet lower, and Rend Lake was at about the same level as at the end of December. At the end of January, Lake Shelbyville was 0.1 foot above the winter target level, Carlyle Lake level was 0.3 feet above the winter target level, and Rend Lake was 1.1 feet below the spillway level.
Great Lakes. Current month mean and end-of-month values are provisional and are relative to International Great Lakes Datum 1985. The January 2026 mean level for Lake Michigan was 577.5 feet. The monthly mean level one year ago (January 2025) was 578.0 feet. The long-term average lake level for January is 578.5 feet, based on 1918-2024 data. In this period of record, the lowest mean level for Lake Michigan for January occurred in 2013 at 576.0 feet, and the highest mean level for January occurred in 2020 at 581.6 feet. The month-end level of Lake Michigan was 577.4 feet. All values are provided by the U.S. Army Corps of Engineers Detroit District.
Groundwater Information (Jennie Atkins)
Water tables fell across Illinois in January, ending the month averaging 0.31 feet lower than December.
Eighteen of the twenty-three reporting wells had lower water levels at the end of the month. The Brownstown (Fayette County) and Perry (Pike County) wells had the largest declines, ending the month 2.42 and 2.70 feet lower respectively.
The only significant increase was at the Fermi Lab well (DuPage County). It ended the month 6.29 feet higher than December and 1.80 feet above January 2025.
However, all wells were below the 15 and long-term record. January was the thirteenth month in a row with water tables averaging below the long-term record.
Wells averaged 3.03 feet below January 2025, 3.68 feet below the 15-year average, and 3.68 feet below the long-term record (Table 4).
Data sources for the IWCS include the following:
CPC - Climate Prediction Center
ISWS - Illinois State Water Survey
MRCC - Midwestern Regional Climate Center
NCEI - National Centers for Environmental Information
NWS – National Weather Service
SPC – Storm Prediction Center
USACE – U.S. Army Corps of Engineers
USDM – US Drought Monitor
USGS – US Geological Survey
WARM – Water and Atmospheric Resources Monitoring Program