October 2022 Overview
October temperatures and precipitation were below the long-term average in Illinois. Mean streamflow statewide was below the median for the month. Shallow groundwater levels were below the long-term depths.
Air temperatures averaged 53.4 degrees F, 1.4 degrees below the 1991–2020 normal for October (Figure 1). October average temperatures ranged from the upper 40s in northern Illinois to the mid-50s in southern Illinois, between 1 and 4 degrees below normal.
Precipitation statewide in October was 2.15 inches, 1.11 inches below the long-term statewide average (Figure 1). October total precipitation ranged from over 4 inches in southwest Illinois to less than 1.5 inches in far northwest Illinois.
Soil moisture at 2 inches rose 40 percent in October to a state average of 0.28 water fraction by volume (wfv). Levels at 4 and 8 inches rose 42 and 12 percent, respectively. Moisture levels declined 6 percent at 20 inches and remained steady at 39 and 59 inches.
Mean provisional streamflow aggregated statewide was below the long-term median flow for October, about 85 percent of median (Figure 1). Monthly mean discharge values in October ranged mostly from below normal to normal.
Water surface levels at the end of October were below the full pool or target level at 14 of 20 reporting reservoirs. At the end of October, Lake Shelbyville was 0.8 feet below the seasonal target level, Carlyle Lake was 0.1 foot below the seasonal target level, and Rend Lake was 0.2 feet above the spillway level. Lake Michigan’s mean level was above its long-term mean for the month.
Shallow groundwater levels were 1.1 feet below the long-term average at the end of October (Figure 1). Levels averaged 0.7 feet below those in September and 0.3 feet below last year’s levels.
The following description of temperatures, precipitation, 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.
October in Illinois was cooler and drier than normal in Illinois.
Temperatures averaged 53.4 degrees F, 1.4 degrees below the 1991–2020 normal for October (Table 1). October average temperatures ranged from the upper 40s in northern Illinois to the mid-50s in southern Illinois, between 1 and 4 degrees below normal (Figure 2). The warmest place in the state last month was Olmsted in Pulaski County with an average October temperature of 58.9 degrees. The coolest place was Elizabeth in Jo Daviess County with an average October temperature of 49.2 degrees.
Daily high maximum temperature records were broken last month at 8 stations, and daily high minimum temperature records were broken at 1 station. Daily low minimum temperature records were broken at 17
stations. Cairo tied its all-time October low minimum temperature record with a 25-degree low on October 19.
Overall, October was the 42nd coolest on record statewide.
Precipitation statewide in October was 2.15 inches, 1.11 inches below the long-term statewide average (Table 1). October total precipitation ranged from over 4 inches in southwest Illinois to less than 1.5 inches in far northwest Illinois (Figure 3). The Interstate 55 corridor between St. Louis and Chicago was the only part of the state near to slightly wetter than normal, whereas northwest and southern Illinois were 1 to 3 inches drier than normal. Overall, October was the 47th driest on record statewide.
Drought: The dryness in southern Illinois was part of a larger pattern for the Ohio
and Lower Mississippi River basins. In fact, the entire Lower Ohio valley from Louisville to Cairo only picked up 0.60 inches of total rainfall on average between September 1 and October 21. The exceedingly dry conditions contributed to very low flows and navigation issues along the Ohio and Mississippi Rivers. Extremely dry soils, particularly in southern Illinois, also increased the risk of fire and forced multiple counties to impose burn bans for most of the month. Despite the bans, several wildfires and field fires broke out in southern and central Illinois in October, including a fire that burned at least 115 acres in Jefferson County.
One benefit of the persistently dry conditions was that it aided a relatively smooth harvest. On the other hand, low-flow and navigation issues along the Mississippi River from the dry weather have contributed to higher transportation costs and grain storage issues.
Illinois Climate Network (ICN) (Jennie Atkins)
The Illinois Climate Network (ICN) consists of 19 stations across the state that collect hourly weather and soil information.
Wind speeds averaged 6.2 mph in October, 1.7 mph higher than in September but 0.4 mph lower than the month’s long-term average. ICN Stelle (Ford County) continues to have the highest monthly average at 10.0 mph. ICN Monmouth (Warren County) had the highest recorded wind gust, measuring 41.0 mph on October 13.
Temperatures declined 13 degrees from in September to an average of 53 degrees, 1 degree below the long-term average. Station highs ranged from the high 70s to mid-80s with station lows in the 20s. The month’s highest temperature was 84 degrees, recorded at ICN Perry (Pike County) on October 22. The lowest was 21 degrees, measured at ICN Monmouth on October 19.
Soil temperatures averaged in the mid-50s, 13 to 15 degrees cooler than in September. Under bare soils, temperatures ranged from 33 to 86 degrees at 2 inches and 35 to 80 degrees at 4 inches. Temperatures under sod ranged from 41 to 74 degrees at 4 inches and 46 to 74 degrees at 8 inches.
Precipitation averaged 2.21 inches, 0.14 inches less than in September and 0.74 inches lower than the long-term average. The southern stations had a dry month until the last week. ICN Carbondale (Jackson County) received 1.10 inches of rain between October 25 and 31, 87 percent of its monthly total of 1.27 inches. This station ended the month with a deficit of more than 2 inches.
Most stations had a drier than normal month. However, ICN Stelle (Ford County) and ICN Snicarte (Mason County) ended with monthly totals of 3.53 inches and 3.55 inches, respectively, the highest of the month.
Rain at the end of October caused soil moisture to rise across the network. Soil moisture at 2 inches rose 75 percent on average during the last seven days of the month. The most significant increases were in the dry south where levels doubled in the last week. Overall, soil moisture rose 40 percent in October to an end-of-month average of 0.28 water fraction by volume (wfv).
Similar increases were seen at 4 and 8 inches. However, the rain did not impact the deeper depths. Soil moisture at 20 inches declined an average of 8 percent for the month, while levels remained steady at 39 and 59 inches.
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; at some stations, the available record may not be continuous. Additional source data may be available from the 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 below the median value for October (approximately 85 percent of the median) and below the mean for October (approximately 40 percent of the mean). Monthly mean discharge values in October ranged mostly from 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 an 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-September water levels at 20 reservoirs for which levels were reported last month and this month, reported end-of-October water levels were lower at 11 reservoirs, higher at 4 reservoirs, and about the same as at the end of September at 5 reservoirs. For the 20 reservoirs with measurements reported at the end of October, water levels were below normal target pool or spillway level at 14 reservoirs and above normal target pool or spillway level at 6 reservoirs.
Major Reservoirs. Compared to water levels at the end of September, at the end of October the water level at Lake Shelbyville was 0.3 feet lower, Carlyle Lake was 0.3 feet lower, and Rend Lake was 0.8 feet lower. At the end of October, Lake Shelbyville was 0.8 feet below the seasonal target level, Carlyle Lake was 0.1 foot below the seasonal target level, and Rend Lake was 0.2 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 October 2022 mean level for Lake Michigan was 579.4 feet. The monthly mean level one year ago (October 2021) was 580.3 feet. The long-term average lake level for October is 578.9 feet, based on 1918–2021 data. In this period of record, the lowest mean level for Lake Michigan for October occurred in 1964 at 576.4 feet, and the highest mean level for October occurred in 1986 at 582.4 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)
Despite improvements in soil moisture, water table levels continued to decline across Illinois in October. Twenty-five out of the 26 wells monitored reported lower levels at the end of the month. The Freeport well (Stephenson County) had the largest decrease with a level of 1.3 feet below that in September.
Overall, well levels averaged 0.7 feet below September levels, ranging from 1.3 feet below to 0.6 feet above.
Levels were more of a mixed bag when compared to last year. Water tables averaged 0.3 feet less than in October 2021 and ranged from 8.0 feet below to 4.5 feet above. Wells, especially in northern Illinois, have shown marked improvements over the past year. At the end of October, the Freeport well was 2.2 feet above the 2021 level despite decreases in the past month, while the Mt. Morris well (Ogle County) was 4.5 feet above last year’s level.
In central Illinois, however, several wells had declines of 5 feet or more. The Bondville ICN well (Champaign County) ended the month 7.6 feet lower than in 2021, and the Good Hope well (McDonough County) was 7.9 feet lower than last year’s level.
Levels averaged 1.1 feet below the 15-year average and 1.7 feet below 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