March 2025 Overview
March was warmer and drier for Illinois.
Temperatures were 6.3° above normal for the month, averaging 47.7°F. March 2025 was the 7th warmest March on record for the state.
Precipitation averaged 2.76 inches, 0.18 inches below normal. The month was the 58th driest March on record.
Mean streamflow statewide was below the median for the month.
Mean provisional streamflow aggregated statewide was below the long-term median flow for March, about 55% of median (Figure 1). Monthly mean discharge values in March ranged from much below normal to normal.
Water surface levels at the end of March were below the full pool or target level at 10 of 20 reporting reservoirs. At the end of March, Lake Shelbyville was 1.3 feet below the April 1 target level, Carlyle Lake level was 0.3 feet above the April 1 target level, and Rend Lake was 3.5 feet above the spillway level.
Lake Michigan’s mean level was below its long-term mean for the month.
Shallow groundwater levels were 1.14 feet below the long-term average at the end of March. Levels averaged 0.70 feet above February and 0.42 feet below last year.
Weather/Climate Information (Trent Ford)
The following description of temperatures, modified growing degree days, precipitation, severe weather, and drought comes from data compiled by networks that report to the National Oceanic and Atmospheric Administration (NOAA). These data are provisional and may change slightly over time.
March in Illinois was much warmer and slightly drier than normal.
Temperatures averaged 47.7°F, 6.3° above the 1991-2020 normal for March and the 7th warmest March on record statewide (Table 1). March average temperatures ranged from the low 40s in northern Illinois to the mid-50s in southern Illinois, between 2 and 7 degrees above normal (Figure 2). Multiple waves of late spring-like weather brought temperatures reaching well into the 80s across the state, including 83 in Quincy and Decatur. Very cold weather, while fleeting, did bring temperatures well below freezing across the state, including nighttime low temperatures of 10 degrees in Lincoln and 12 degrees in Rockford. The coldest place in the state last month was Elgin with an average of 40.9 degrees, while the warmest was Smithland Lock and Dam in Massac County with an average of 53.1 degrees.
The milder weather broke 71 daily high maximum temperature records in Illinois and 13 daily high minimum temperature records. Meanwhile, no daily low minimum or low maximum temperature records were broken in Illinois last month.
Precipitation statewide in March was 2.76 inches, 0.18 inches below normal and the 58th driest March on record statewide (Figure 3, Table 1). Total precipitation ranged from less than 1.5 inches in far southwest Illinois to over 8 inches in northeast Illinois. The northern half of the state was 1 to 4 inches wetter than normal last month, while most areas south of Interstate 64 were 1 to 3 inches drier than normal (Figure 3).
Severe Weather: While severe weather, including thunderstorms, strong winds, hail, and tornadoes, occur every month in Illinois, they tend to be most common between March and July. An active storm track and abundant moist, warm air from the Gulf of Mexico produced multiple severe weather outbreaks in March across the Midwest. In all, there were 58 tornado warnings issued in Illinois, the most on record for March. The NOAA Storm Prediction Center lists 33 tornado reports in Illinois last month, which may be adjusted before a final number is released. Included in these reports is a confirmed EF-2 tornado that caused significant damage to Neoga High School in Cumberland County on March 15, and multiple tornadoes that damaged or destroyed buildings in Douglas County on March 30.
Snow: As is the case in most years, March precipitation came in many forms, including snow. However, measurable snowfall was mostly contained to the northern third of the state. Monthly snowfall totals in those places that were able to measure the snow ranged from around 2 inches in the Quad Cities region to over 7 inches in parts of Knox County and Boone County in western and northern Illinois, respectively.
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 9.0 mph, 1.2 mph higher than February and 0.4 mph higher than the long-term average. ICN Bondville (Champaign County) had March’s highest average, 13.9 mph. The highest measured wind gust was 60.1 mph, recorded at ICN DeKalb (Dekalb County) on March 14.
Temperatures averaged 18° higher than February, averaging 48° for the month. Station highs where in the high 70s and low 80s. Station lows ranged from the low teens to the low 20s. The highest recorded temperature was 84°, measured at ICN Dixon Springs (Pope County). The lowest was 11°, recorded at ICN St Charles (Kane County).
Soil temperatures in the mid-40s at all depths, 10 – 12° higher than February. Under bare soils, temperatures ranged from 27 to 79° at 2 inches and 31 to 70° at 4 inches. Temperatures under sod ranged from 32 to 65° at 4 inches and 31 to 62° at 8 inches.
March precipitation averaged 2.87 inches, 1.50 inches more than February but 0.15 inches lower than the long-term average. The highest total was 4.05 inches at ICN Belleville (St Clair County) while the lowest was 1.93 inches at ICN Carbondale (Jackson County).
Surface Water Information (Bill Saylor)
Provisional monthly mean flows for this month for 26 streamgaging stations located throughout Illinois are shown in Table 2, compared to statistics of past record of monthly mean flows at those stations for the same month. Both recent and long-term data are retrieved from USGS online data services following the end of the month. Years of record values in Table 2 represent the number of past monthly values included in the Table 2 statistics; at some stations, the available record may not be continuous. Additional source data may be available from USGS.
The statewide percent of historical mean flow and percent of historical median flow are calculated by dividing the sum of the average flows this month at stations in Table 2 by the sum of the historical mean and median flows calculated for the month, respectively, at the same stations. This method is intended to weigh individual observations proportionately in the aggregate comparison. (The Illinois River and Rock River stations are excluded from the statewide calculation because other rivers listed in Table 2 contribute to their flow.)
Mean provisional flow aggregated statewide, using the available monthly mean data shown this month in Table 2, was below the median value for March (approximately 55 percent of the median) and below the mean for March (approximately 45 percent of the mean). Monthly mean discharge values in March ranged from much below normal to normal.
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-February water levels at 19 reservoirs for which levels were reported last month and this month, reported end-of-March water levels were lower at 2 reservoirs, higher at 10 reservoirs, and about the same as at the end of February at 7 reservoirs. For the 20 reservoirs with measurements reported for the end of March, water levels were below normal target pool or spillway level at 10 reservoirs, above normal target pool or spillway level at 8 reservoirs, and at about the target level or spillway level at 2 reservoirs.
Major Reservoirs. Compared to water levels at the end of February, at the end of March the water level at Rend Lake was 0.9 feet lower, Carlyle Lake was 0.8 feet higher, and Lake Shelbyville was at about the same level as a month prior. At the end of March, Lake Shelbyville was 1.3 feet below the April 1 target level, Carlyle Lake level was 0.3 feet above the April 1 target level, and Rend Lake was 3.5 feet above the spillway level. (Target operating levels at Lake Shelbyville and Carlyle Lake increase from March to May.)
Great Lakes. Current month mean and end-of-month values are provisional and are relative to International Great Lakes Datum 1985. The March 2025 mean level for Lake Michigan was 577.9 feet. The monthly mean level one year ago (March 2024) was 578.7 feet. The long-term average lake level for March is 578.5 feet, based on 1918-2023 data. In this period of record, the lowest mean level for Lake Michigan for March occurred in 1964 at 576.1 feet, and the highest mean level for March occurred in 2020 at 581.4 feet. The month-end level of Lake Michigan was 578.1 feet. All values are provided by the U.S. Army Corps of Engineers Detroit District.
Groundwater Information (Jennie Atkins)
Water tables were 0.70 feet higher at the end of March as nineteen of twenty-four reporting wells reporting increases.
The Fermi Lab well (DuPage County) rose 6.45 feet, the highest for the month. However, despite the increase, the well was 1.18 feet lower than last year.
Decreases were seen at five wells at the end of the month. In southern Illinois, the Southeast College well (Saline County) and Carbondale well (Jackson County) were 1.85 and 1.34 feet lower, respectively.
Wells averaged 0.42 feet below March 2024, 1.34 feet below the 15-year average, and 1.14 feet below the long-term record (Table 4).
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/