March 2022 Overview
Temperatures and precipitation were above the long-term average in Illinois in March. Mean streamflow statewide was above the median for the month. Shallow groundwater levels were above the long-term depths.
Air temperatures averaged 43.3 degrees F, 1.9 degrees above the 1991–2020 normal for March (Figure 1). March average temperatures ranged from the high 30s in northern Illinois to the high 40s in southern Illinois, between 1 and 4 degrees above the 1991–2020 normal.
Precipitation statewide in March was 4.30 inches, 1.36 inches above the long-term statewide average (Figure 1). March total precipitation ranged from just over 3 inches in northern Illinois to nearly 6 inches in south-central Illinois, between one-half and 3 inches above the 1991–2020 normal.
Mean provisional streamflow aggregated statewide was above the long-term median flow for March, about 135 percent of median (Figure 1). Monthly mean discharge values in March were below normal in far northern Illinois, above normal across south-central Illinois, and normal elsewhere in Illinois.
Water surface levels at the end of March were below the full pool or target level at 1 of 22 reporting reservoirs. At the end of March, Lake Shelbyville was 5.4 feet above the April 1 target level, the Carlyle Lake level was 3.4 feet above the April 1 target level, and Rend Lake was 5.2 feet above the spillway level. Lake Michigan’s mean level was above its long-term mean for the month.
Shallow groundwater levels were 0.72 feet above the long-term average at the end of March (Figure 1). Levels averaged 0.87 feet above February levels and 0.06 feet above last year’s levels.
Weather/Climate Information
The following description of temperatures, 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 warmer and wetter than average statewide.
Temperatures averaged 43.3 degrees F, 1.9 degrees above the 1991–2020 normal for March (Table 1). March average temperatures ranged from the high 30s in northern Illinois to the high 40s in southern Illinois, between 1 and 4 degrees above the 1991–2020 normal (Figure 2). Several stations saw high temperatures in the high 70s early in the month and even highs of over 80 degrees in St. Clair and Randolph counties. Meanwhile, many places in northern and central Illinois saw nighttime low temperatures in the single digits, including 3 degrees in Knox County.
Daily high maximum temperature records were broken at 14 stations in March, and daily high minimum temperature records were broken at 1 station. Daily low maximum temperature records were broken at 11 stations and daily low minimum temperature records were broken at 9 stations last month.
Precipitation statewide in March was 4.30 inches, 1.36 inches above the long-term statewide average (Table 1). March total precipitation ranged from just over 3 inches in northern Illinois to nearly 6 inches in south-central Illinois, between one-half and 3 inches above the 1991–2020 normal. Stations in Alton, Mt. Vernon, and Mattoon received more than 7 inches of precipitation in March, over 4 inches above normal.
Snow: Only western Illinois had above normal March snow accumulation. Overall, March total snowfall ranged from over 4 inches in northern Illinois to less than a tenth of an inch in south-central Illinois.
Drought: Although the March precipitation was a bit lighter in northern and northwest Illinois, the late-month precipitation considerably improved drought conditions. The U.S. Drought Monitor improved the McHenry and Lake County listing from severe to moderate drought and completely removed the drought categorization in parts or all of Mercer, Henry, and Lee counties.
Illinois Climate Network (ICN) (Jennie Atkins)
The Illinois Climate Network (ICN) collects hourly weather and soil information from 19 stations across the state.
Wind speeds averaged 8.4 mph across the network in March, equal to the February average and 0.2 mph below the long-term average. ICN Bondville in Champaign County had the month’s highest average wind speed at 13.1 mph. The highest wind gust was 52.4 mph, recorded at ICN Stelle in Ford County on March 25.
Air temperatures arose 14 degrees F from in February to a network average of 43 degrees, equal to the long-term average. Highs were in the 70s for most stations with the month’s highest temperature at 80 degrees, recorded at ICN Belleville in St. Clair County on March 2. Lows were in the single digits and teens. March’s lowest temperature was 5 degrees, measured on March 12 at ICN Freeport in Stephenson County.
Soil temperatures rose 9 to 11 degrees in March to averages in the low to mid-40s. Temperatures were 1–2 degrees below the long-term averages. Under bare soil, temperatures ranged from 22 to 77 degrees at 2 inches and 27 to 67 degrees at 4 inches. Temperatures under sod ranged from 31 to 61 degrees at 4 inches and 31 to 56 degrees at 8 inches.
Precipitation was above the long-term averages at all ICN stations in March. The network averaged 4.53 inches for the month, 0.85 inches more than in February and 1.82 inches higher than the network’s long-term average.
The northern stations received a much-needed increase in precipitation. ICN Freeport had a total of 3.51 inches in March, 270 percent more than in January and February combined.
Soil moisture data will return to the IWCS in Spring 2022.
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 U.S. Geological Survey (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. The available record may not be continuous at some stations. 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 weight 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 above the median value for March (approximately 135 percent of the median) and above the mean for March (approximately 115 percent of the mean). Monthly mean discharge values in March were below normal in far northern Illinois, above normal across south-central Illinois, and normal elsewhere in 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-February water levels at 22 reservoirs for which levels were reported last month and this month, reported end-of-March water levels were lower at 6 reservoirs, higher at 14 reservoirs, and about the same as at the end of February at 2 reservoirs. For the 22 reservoirs with measurements reported at the end of March, water levels were below normal target pool or spillway level at 1 reservoir, above normal target pool or spillway level at 18 reservoirs, and at about full pool level at 3 reservoirs.
Major Reservoirs. Compared to water levels at the end of February, at the end of March the water level at Lake Shelbyville was 1.5 feet lower, Carlyle Lake was 2.6 feet lower, and Rend Lake was 0.1 foot lower. At the end of March, Lake Shelbyville was 5.4 feet above the April 1 target level, the Carlyle Lake level was 3.4 feet above the April 1 target level, and Rend Lake was 5.2 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 March 2022 mean level for Lake Michigan was 579.2 feet. The monthly mean level one year ago (March 2021) was 580.5 feet. The long-term average lake level for March is 578.5 feet, based on 1918–2021 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 579.3 feet. All values are provided by the U.S. Army Corps of Engineers Detroit District.
Groundwater Information (Jennie Atkins)
Water tables rose at most monitoring wells in March. Seventy-six percent of monitored wells reported an increase as levels rose an average of 0.87 feet from February’s average. Levels ranged from 0.86 feet below to 3.12 feet above those of last month.
Increased precipitation in northern Illinois caused water levels to rise regionally. The Freeport well rose 2.31 feet in March, the first increase since April 2021. However, despite the increase, the water table remained lower than normal, ending the month 8.99 feet lower than in March 2021 and 6.10 feet below the 15-year average.
Statewide water levels averaged 0.06 feet above 2021 levels, 0.37 feet above the 15-year average, and 0.72 feet above the period of record.
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://www.isws.illinois.edu/warm