January 2025 Overview
January was cold and dry for Illinois.
Temperatures averaged 23.0°F, 3.7° below the 1991-2020 normal and the 38th coldest January on record.
Precipitation averaged 1.15 inches, 1.16 inches below the long-term statewide average and the 25th driest January on record statewide.
Mean provisional streamflow data was sufficiently limited, due to winter conditions, to preclude estimating an aggregate mean streamflow condition statewide for January.
Water surface levels at the end of January were below the full pool or target level at 5 of 20 reporting reservoirs. At the end of January, Lake Shelbyville was 2.4 feet above the February 1 target level, Carlyle Lake level was 0.5 feet above the February 1 target level, and Rend Lake was 3.4 feet above the spillway level.
Lake Michigan’s mean level was below its long-term mean for the month.
Shallow groundwater levels were 0.48 feet below the long-term average at the end of January. Levels averaged 0.09 feet above December and 1.05 feet below last year.
Weather/Climate Information (Trent Ford)
January in Illinois was much cooler and drier than normal.
Temperatures averaged 23.0°F, 3.7° below the 1991-2020 normal for January (Table 1, Figure 2). Last month was the 38th coldest January on record statewide.
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.
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.
Precipitation statewide in January was 1.15 inches, 1.16 inches below the long-term statewide average (Table 1, Figure 3). Last month was the 25th driest January on record statewide. 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 3).
Snow: Depending on who you talk to, January 2025 was either a very active winter weather month or quite boring. 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. 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.
Illinois Climate Network (ICN) (Jennie Atkins)
The Illinois Climate Network (ICN) consists of 19 stations across the state which collects hourly weather and soil information.
Winds averaged 7.7 mph in January , 0.1 mph higher than December but 0.6 mph lower than the network’s long-term average. ICN Monmouth (Warren County) was the windiest with a monthly average of 12.4 mph. The highest measured wind gust was 39.0 mph, measured at ICN DeKalb (DeKalb County) on January 28.
Temperatures were 11° lower than December with a network average of 24°. Station highs ranged from the high 40s to low 60s with lows from the negative teens to the single digits. The month’s high was 61°, measured at ICN Dixon Springs (Pope County) on January 31. ICN Freeport (Stephenson County) had the month’s low with a temperature of -15° on January 21.
Soil temperatures fell 5 to 6° to averages in the low to mid 30s. Under bare soils, temperatures ranged from 6 to 59° at 2 inches and 12 to 51° at 4 inches. Temperatures under sod ranged from 23 to 48° at 4 inches and 26 to 50° at 8 inches.
Precipitation averaged 1.73 inches, 1.62” less than December and 0.60” lower than the long-term average. Seven stations, all in central Illinois, recorded less than an inch for the month. Only five stations, in the far south and north-east, had monthly totals equal or greater to their long-term averages. ICN Dixon Springs (Pope County) had the wettest month again in January with a total of 5.22”, bringing its total for this winter up to 12.78”.
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 or to estimate an aggregate mean streamflow condition statewide for January.
Water-Supply Lakes and Major Reservoirs. Table 2 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 2 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 2. For some reservoirs, this average does not include additional period of record prior to a substantial change in reservoir operation. Most reservoirs in Table 2 serve as public water supplies, with the exceptions noted in the last column.
Compared to end-of-December water levels at 18 reservoirs for which levels were reported last month and this month, reported end-of-January water levels were lower at 9 reservoirs, higher at 5 reservoirs, and about the same as at the end of December at 4 reservoirs. For the 20 reservoirs with measurements reported for the end of January, water levels were below normal target pool or spillway level at 5 reservoirs, above normal target pool or spillway level at 13 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 4.0 feet lower, Carlyle Lake was 1.1 feet lower, and Rend Lake was 0.6 feet higher as a month prior. At the end of January, Lake Shelbyville was 2.4 feet above the February 1 target level, Carlyle Lake level was 0.5 feet above the February 1 target level, and Rend Lake was 3.4 feet above 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 2025 mean level for Lake Michigan was 578.0 feet. The monthly mean level one year ago (January 2024) was 578.8 feet. The long-term average lake level for January is 578.5 feet, based on 1918-2023 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 577.9 feet. All values are provided by the U.S. Army Corps of Engineers Detroit District.
Groundwater Information (Jennie Atkins)
Water tables averaged 0.09’ higher at the end of January. Thirteen of twenty-two monitored wells recorded increases at the end of the month. Most well levels changed less than 1’ over the month with 27% recording changes of 0.1’ or less.
There were notable differences when compared to January 2024 levels. Wells in central and northern Illinois are significantly lower than last year. The Good Hope well (McDonough County) and Janesville well (Coles County) had the largest declines with levels 8.24 and 7.73’, respectively, lower than 2024, . Most southern wells, however, were higher. Most notably the Belleville well (St Clair County) was 11.97’ higher at the end of January than last year.
Wells averaged 1.05 feet above January 2024, 0.48 feet below the 15-year average, and 0.46 feet below the long-term record (Table 3).
Data sources for the IWCS include the following:
CPC - Climate Prediction Center, https://www.cpc.ncep.noaa.gov/index.php
ISWS - Illinois State Water Survey, https://www.isws.illinois.edu
MRCC - Midwestern Regional Climate Center, https://mrcc.purdue.edu/
NCEI - National Centers for Environmental Information, https://www.ncei.noaa.gov
NWS - National Weather Service, https://www.nws.noaa.gov
SPC - Storm Prediction Center, https://www.spc.noaa.gov
USACE - U.S. Army Corps of Engineers, https://www.lre.usace.army.mil
USDM - U.S. Drought Monitor, https://droughtmonitor.unl.edu
USGS - U.S. Geological Survey, https://waterdata.usgs.gov/il/nwis
WARM - Water and Atmospheric Resources Monitoring Program, https://warm.isws.illinois.edu/warm/