June 2025 Overview
June was warmer and drier for Illinois.
Temperatures averaged 74.3°, 2.1° warmer than normal. It was the 20th warmest June on record for Illinois (Figure 1).
Precipitation statewide in June was 4.07 inches, 0.58 inches below normal and the 57th wettest on record (Figure 1).
Mean streamflow statewide was approximately equal to the median for the month.
Mean provisional streamflow aggregated statewide was approximately equal to the long-term median flow for June, about 100% of median (Figure 1). Monthly mean discharge values in June were mainly normal for the month.
Water surface levels at the end of June were below the full pool or target level at 5 of 20 reporting reservoirs. At the end of June, Lake Shelbyville was 0.3 feet above the summer target level, Carlyle Lake level was 0.2 feet above the summer 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.
Soil moisture at 2-inch depths averaged 0.23 water fraction by volume (wfv) at the end of June, 11% lower than the beginning of the month. Only the northern region showed an increase. Declines were seen through the top 20 inches with little change at the 39- and 59-inch depths.
Shallow groundwater levels were 1.53 feet below the long-term average at the end of June. Levels averaged 0.54 feet below May and 0.02 feet above last year (Figure 1).
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 drier than normal statewide.
Temperatures averaged 74.3° in June, 2.1° above normal and the 20th warmest June on record statewide (Table 1). June began with largely cooler weather. However, a major pattern change around mid-month brought in much warmer and humid air from the south and southwest. The result was a significant increase in temperatures, such that virtually every day in the latter half of the month was warmer than normal statewide, many of which were 5 to 12° warmer than normal. The heat wave in late June was extreme in both its intensity – especially nighttime temperatures – and its duration. High humidity not only pushed afternoon heat index values well above 100° across the state on multiple days but also kept nighttime temperatures well above normal. The average nighttime low in the last week of June was the highest on record in many places across the Midwest, including in Chicago and Peoria. In fact, the average temperature in Chicago between June 23 and June 30 was similar to the average temperature this time of the year in Orlando, Florida.
Overall, June average temperatures ranged from the low 70s in northern Illinois to the high 70s in southern Illinois, 2 to 5° above normal (Figure 2). Most places had daytime high temperatures that reached into the low to mid-90s for much of the last 10 days of the month. However, below average temperatures in early June brought in a few sub-50-degree nighttime lows in central and northern Illinois. In this way, June was the epitome of a transition month from spring to summer. The warmest place in the state last month was Olmsted, Illinois in Pulaski County with an average temperature of 77.3°. The coolest place in the state last month was Barrington in northeast Illinois with an average temperature of 69.9°.
Precipitation statewide in June was 4.07 inches, 0.58 inches below normal and the 57th wettest on record.
June is typically one of the wettest months of the year in Illinois. In some years, June precipitation is consistent across the state, often the case in the wettest of Junes. Last month, however, was more inconsistent. An active storm track across southern Illinois persisted from May into the first two weeks of June, bringing wet weather to much of far southern Illinois. A large ridge established in the eastern U.S. in mid-June, impeding widespread heavy precipitation. Isolated thunderstorms and showers repeatedly popped up, especially in northern Illinois, in the last week of the month; however, most of central and southern Illinois remained on the dry side.
The result of the decidedly variable precipitation last month was a wide range in totals, from less than 3 inches in parts of south-central and east-central Illinois to over 10 inches in southeast Illinois (Figure 3). Most of the state north of highway 13 was near to 2-3 inches drier than normal in June, with the largest departures in the upper Kaskaskia River watershed. Meanwhile, most of far southern Illinois was 1 to 6 inches wetter than normal last month, with the largest departures along the Ohio River.
Drought: The most June rain fell in places that didn’t really need it, like in far southern Illinois. However, the isolated thunderstorms and showers in late June were beneficial in northern Illinois, especially along and just south of the Wisconsin border. U.S. Drought Monitor maps from the start and end of June show some improvement in northern and western Illinois, thanks to those beneficial showers.
Severe Weather: June is one of our most active severe weather months, and last month followed suit. The NOAA Storm Prediction Center preliminary June data includes 26 tornado reports, 82 severe wind reports, and 2 severe hail reports. Among these was an EF-2 tornado that damaged several buildings and trees in Morgan County, and a long-track EF-1 that did damage around and in the Quad Cities. Severe wind was the most common form of severe weather last month, as is often the case. A line of strong storms in the third week of the month caused significant wind damage to buildings and trees across central Illinois, and laid down many acres of corn, although most reports indicate very limited permanent crop damage from these storms. Thankfully, hail was sparser in Illinois.
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 5.2 mph, 1.4 mph lower than May and 0.7 mph lower than the network’s long-term average. ICN Monmouth (Warren County) was the windiest station for the month with the highest average, 8.3 mph, and the highest recorded wind gust, 46.1 mph measured on June 3.
Temperatures rose 12.1° from May to an average of 74.5°, 1.9° above the long-term average. Station highs were in the 90s with lows from the 50s to the 30s. The month’s highest temperature was 96.8°, recorded at ICN Rend Lake (Jefferson County) on June 24. The lowest was 38.7°, measured on June 1 at ICN St Charles (Kane County).
Soil temperatures rose 10 to 12° to averages in the mid to high 70s. Under bare soils, temperatures ranged from 50.6 to 111.4° at 2 inches and 54.4 to 113.6° at 4 inches. Temperatures under sod ranged from 48.0 to 97.5° at 4 inches and 58.5 to 89.8° at 8 inches.
Precipitation averaged 4.45 inches in June, 0.36 inches higher than the long-term average. The heaviest precipitation was in far southern Illinois where ICN Dixon Springs (Pope County) recorded 8.37 inches. The station has received 41.91 inches in the first half of 2025, 16.45 inches greater than the long-term average.
Soil moisture at 2 inches declined 11% overall in June to a state average of 0.23 water fraction by volume (wfv). Only northern Illinois showed an increase; however, regional moisture levels remained near wilting point.
Soil moisture declined in the first 20 inches. Levels remained high at 39- and 59-inch depths.
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 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 near the median value for June (approximately 100 percent of the median) and below the mean for June (approximately 70 percent of the mean). Monthly mean discharge values at most Table 4 streamgage locations were normal for June. Monthly mean streamflow of the Cache River at Forman in southern Illinois was much above normal in June.
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-May water levels at 18 reservoirs for which levels were reported last month and this month, reported end-of-June water levels were lower at 11 reservoirs, higher at 5 reservoirs, and about the same as at the end of May at 2 reservoirs. For the 20 reservoirs with measurements reported for the end of June, water levels were below normal target pool or spillway level at 5 reservoirs, above normal target pool or spillway level at 11 reservoirs, and at about the target level or spillway level at 4 reservoirs.
Major Reservoirs. Compared to water levels at the end of May, at the end of June the water level at Lake Shelbyville was 0.3 feet lower, Carlyle Lake was 0.2 feet lower, and Rend Lake was 1.0 foot lower. At the end of June, Lake Shelbyville was 0.3 feet above the summer target level, Carlyle Lake level was 0.2 feet above the summer 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 June 2025 mean level for Lake Michigan was 578.8 feet. The monthly mean level one year ago (June 2024) was 579.6 feet. The long-term average lake level for June is 579.3 feet, based on 1918-2023 data. In this period of record, the lowest mean level for Lake Michigan for June occurred in 1964 at 576.6 feet, and the highest mean level for June 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)
Water tables declined 0.54 feet in June with twenty-one of the twenty-four reporting wells lower at the end of the month.
Most wells decreased by less than a foot. However, the Southeast College well (Saline County) fell 2.35 feet in June, the month’s largest decline.
Fourteen wells reported levels lower than a year ago. The greatest differences were the Freeport (Stephenson County) and Mt Morris (Ogle County) wells with each having levels more than seven feet lower than June 2024.
June was the sixth consecutive month with water tables averaging lower than the period of record.
Wells averaged 0.02 feet above June 2024, 1.74 feet below the 15-year average, and 1.53 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