July 2025 Overview
It was a warm, wet July in Illinois.
Temperatures averaged 78.4 degrees in July, 3.0 degrees above normal and the 14th warmest July on record statewide.
Precipitation statewide in July was 6.13 inches, 2.07 inches above average and the 8th wettest July on record statewide.
Mean streamflow statewide was above the median for the month.
Mean provisional streamflow aggregated statewide was above the long-term median flow for July, about 165% of median (Figure 1). Monthly mean discharge values in July ranged from below normal to much above normal.
Water surface levels at the end of July were below the full pool or target level at 6 of 18 reporting reservoirs. At the end of July, Lake Shelbyville was 0.5 feet below the summer target level, Carlyle Lake level was 2.2 feet above the summer target level, and Rend Lake was 2.1 feet above the spillway level.
Lake Michigan’s mean level was below its long-term mean for the month.
Soil moisture at 2-inch depths averaged 0.32 water fraction by volume (wfv) at the end of July, 30% higher than the beginning of the month. Increases were seen through 8 inches while levels at 20 inches and deeper remained steady.
Weather/Climate Information (Trent Ford)
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.
June was much warmer and wetter than normal statewide.
Temperatures averaged 78.4 degrees in July, 3.0 degrees above normal and the 14th warmest July on record statewide (Table 1). July average temperatures ranged from the mid-70s in far northern Illinois to the low 80s in south-central Illinois, between 1 and 6 degrees above normal for most of the state (Figure 2). Persistent southwest flow maintained consistently high temperatures and humidity. Some of the more impressive daily high temperatures last month included 98 degrees in Rock Island and 97 in Charleston. The high humidity kept nighttime low temperatures especially high, including 80-degree low temperatures at Rend Lake and Chicago Midway. In fact, the July average daily low temperature was the highest on record in Danville (69.7 degrees) and the second highest on record in Peoria (70.8 degrees).
Precipitation statewide in July was 6.13 inches, 2.07 inches above average and the 8th wettest July on record statewide (Table 1).
The start of the growing season was dry in northern and parts of central Illinois. While the first half of July largely maintained that dry pattern, the second half of the month let loose and washed away drought concerns in much of Illinois. July total precipitation ranged from around 2.5 inches in southwest Illinois to nearly 15 inches in parts of western and south-central Illinois. Most of the state was 1 to 5 inches wetter than normal last month, while parts of east-central and southern Illinois were a bit closer to normal if not slightly drier than normal in July (Figure 3).
Some of the more impressive July rainfall totals include 13.4 inches in Jerseyville and 11.7 inches in Dixon. In contrast, stations in Perry County and eastern Champaign County had just over 2 inches of total rainfall last month, between 2 and 3 inches below normal.
Severe Weather: It seems that every July brings one or more extreme rainfall events that cause significant flooding damage. Unfortunately, last month followed this pattern. The Chicago National Weather Service Office was particularly busy last month, with two very intense rainfall events and associated urban flooding in July. The first of these included a measure of 5.12 inches of rain in just 90 minutes near the United Center in Chicago. Not to be outdone, a second storm produced over 6 inches of rain in around 90 minutes near Midway Airport (Figure 4). A different storm moved over south-central Illinois overnight on July 20th-21st and produced exceptionally heavy rain around the Vandalia and Brownstown areas in Fayette County, including a report of 13.5 in less than 12 hours. All these events caused significant flooding, including many flooded basements in Cook County, inundated fields and crop damage in parts of Fayette County.
Despite the heavy rainfall and storms, we did not have a very active severe weather month in July. The NOAA Storm Prediction Center only reported 1 tornado in Illinois last month, an EF-0 in Fayette County. There were 113 severe wind reports and 10 severe hail reports last month, most of which were in the northern two-thirds of the state. As of August 1, Illinois had an unofficial total of 131 tornadoes in 2025 according to the Storm Prediction Center. This is a preliminary total and may be adjusted later this year as reports are refined. However, if that total is accurate, it would give this year the second highest tornado frequency on record for any year, with only last year (2024) surpassing this total.
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 were lower than normal again in July. Wind speeds averaged 3.9 mph,1.3 mph lower than June and 0.9 mph below the long-term average. ICN Monmouth (Warren County) had the month’s highest average wind speed of 5.9 mph. The highest recorded wind gust was 53.0 mph, measured at ICN Snicarte (Mason County) on July 11.
Temperatures increased 3.3° over June to an average of 77.8°, 2.8° above the long-term average. Station lows ranged from the low 50s to high 60s with highs in the 90s. The highest recorded temperature was 97.0° at ICN Rend Lake (Jefferson County) on July 30. The lowest temperature was 51.5°, measured at ICN DeKalb (DeKalb County) on July 18.
Soil temperatures were 5 to 6° higher in July with averages in the high 70s and low 80s. Under bare soils, temperatures ranged from 60.2 to 110.9° at 2 inches and 65.8 to 114.6° at 4 inches. Temperatures under sod ranged from 69.8 to 98.9° at 4 inches and 90.6 to 70.4° at 8 inches.
July was wet for most of the network as all but three stations recorded totals higher than normal. Overall, the network averaged 6.00 inches for the month, 1.89 inches higher than the long-term average. Three stations, ICN Brownstown (Fayette County), ICN Monmouth (Warren County), and ICN Perry (Pike County), recorded more than 8 inches with Brownstown having July’s highest total at 8.88 inches.
The northern stations received much needed rain in July. ICN Freeport (Stephenson County) measured 6.46 inches in July, increasing its 2025 total to 17.83 inches. The station’s 2025 deficit decreased from 5.71 inches at the end of June to 2.89 inches at the end of July.
ICN Dixon Springs (Pope County) had another wet month. The station reported 6.19 inches for July, 1.46 inches above normal. Its 2025 total was 48.10 inches at the end of the month, 22.40 inches higher than the long-term average.
The higher rain totals led to higher soil moisture at the northern and central stations. Levels in the north more than doubled at 2 inches as regional averages increased from 0.16 to 0.33 water fraction by volume (wfv). In central Illinois, levels were 59% higher at the end of the month.
However in the south, 2-inch soil moisture declined 11 percent on average as soils dried out slightly from the near field capacity levels at the end of June.
Overall, 2-inch soil moisture levels increased 30% in July to a network average of 0.32 wfv. 4- and 8-inch depths also had increases greater than 20%. Moisture levels remained high at the 20-inch depths and greater, showing little change over the month.
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 above the median value for July (approximately 165 percent of the median) and slightly above the mean for July (approximately 110 percent of the mean). Monthly mean discharge values in July ranged from below normal to much above 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 the 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-June water levels at 18 reservoirs for which levels were reported last month and this month, reported end-of-July water levels were lower at 10 reservoirs, higher at 7 reservoirs, and about the same as at the end of June at 1 reservoir. For the 20 reservoirs with measurements reported for the end of July, water levels were below normal target pool or spillway level at 6 reservoirs, above normal target pool or spillway level at 9 reservoirs, and at about the target level or spillway level at 3 reservoirs. Inflow to Sparta Reservoir was supplemented by pumping from the Kaskaskia River. Carlinville water system continues to pump from its second lake, where the lake level was approximately one foot below full pool.
Major Reservoirs. Compared to water levels at the end of June, at the end of July the water level at Lake Shelbyville was 0.7 feet lower, Carlyle Lake was 2.0 feet higher, and Rend Lake was 1.3 feet lower. At the end of July, Lake Shelbyville was 0.5 feet below the summer target level, Carlyle Lake level was 2.2 feet above the summer target level, and Rend Lake was 2.1 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 July 2025 mean level for Lake Michigan was 579.0 feet. The monthly mean level one year ago (July 2024) was 579.8 feet. The long-term average lake level for July is 579.4 feet, based on 1918-2023 data. In this period of record, the lowest mean level for Lake Michigan for July occurred in 1964 at 576.7 feet, and the highest mean level for July occurred in 2020 at 582.2 feet. The month-end level of Lake Michigan was 579.0 feet. All values are provided by the U.S. Army Corps of Engineers Detroit District.
Groundwater Information (Jennie Atkins)
Despite the increases in precipitation and soil moisture, the impacts on the water tables were mixed.
Overall water tables declined 0.02 feet in July with thirteen of the twenty-five reporting wells lower at the end of the month.
Most of the declines were less than 1 foot; however, there were larger declines at the Southeast College (Saline County) and Bondville (Champaign County) wells which were 1.95 and 3.26 feet lower at the end of July, respectively.
Twelve wells rose in July with the largest increase of 3.82 feet at the Perry (Pike County) well.
A wetter July at the Freeport well (Stephenson County) led to a slight increase (0.40 feet) in the well level that has been declining since July 2024. However, the increase in rainfall did not appear to affect the DeKalb well (Dekalb County) which was 2.94 feet lower at the end of the month and continued its four-month decline.
Wells averaged 0.91 feet below June 2024, 1.17 feet below the 15-year average, and 0.83 feet below the long-term record (Table 4). July was the seventh consecutive month with water tables averaging lower than the long-term record.
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