Persistently dry conditions and summer-like temperatures have pushed parts of the state in moderate to severe drought. Drought impacts and condition reports are critical as drought conditions evolve in coming weeks. Please consider reporting what conditions look like in your area using the CMOR system: go.ilinois.edu/cmor.
Current Conditions
Following a top 5 wettest July in Illinois, the tap shut off in August and the first half of September. Most of southern Illinois and parts of northeast and western Illinois have seen less than 2 inches of rain since August 1st, between 2 and 4 inches below normal (Figure 1). At the same time, heat in late August and persistently above normal temperatures in September have worsened dry conditions through more evaporation.
Figure 1. Precipitation across Illinois over the last 30-days ending on September 11th. Maps show (left) 30-day precipitation totals and (right) departures from normal precipitation.
The U.S. Drought Monitor greatly expanded drought and abnormally dry conditions across Illinois in their September 10th update. Roughly 77% of the state is abnormally dry, 20% of the state is now in at least moderate drought, and parts of Alexander, Union, Pulaski, and Massac Counties in southern Illinois are in severe drought (Figure 2).
Figure 2. U.S. Drought Monitor map and statistics as of September 10th (released on September 12th).
Drought Impacts
Drought in mid-September is decidedly different than drought in mid-July, but nonetheless impactful. Agricultural impacts from our current drought situation include deteriorating pasture conditions, moisture stress and potential yield loss in soybeans and late planted corn, and stress from disease and insect pressure that are made worse by dry conditions. The dryness does help progress crop dry-down and timely harvest; however, dry conditions also increase fire risk in fields and adjacent ditches.
This is the time of the year when we typically see the lowest streamflow levels around the state, and the recent dryness has pushed levels and flow well below normal in many streams. The drought affecting Illinois is much worse in Ohio, West Virginia, and eastern Kentucky, and has significantly declined Ohio River flow. Because the lower Mississippi River (south of Cairo) greatly depends on water from the Ohio River, levels along the Mississippi have once again dipped below low stage, threatening barge traffic and other activities along the big river.
Drought impacts and condition reports are critical as drought conditions evolve in coming weeks. Please consider reporting what conditions look like in your area using the Condition Monitoring Observer Reports system: go.ilinois.edu/cmor.
Outlooks
For the second time this year, Illinois may be getting some drought relief from tropical systems. The remnants of Hurricane Francine are forecasted to bring substantial rain to the mid-Mississippi Valley and lower Ohio Valley, including 7-day forecasts of 2-3 inches in southern Illinois (Figure 3).
Figure 3. National Weather Service 7-day precipitation forecast for September 12-19.
The rainfall would be greatly helpful to reducing drought conditions, but more consistent rain is needed in coming weeks to completely assuage concerns of fire and low flow along the major rivers. The Climate Prediction Center’s most recent outlook is bullish toward wetter conditions in Illinois in late September. So, hopefully this current drought is a short-lived problem.
Drought re-intensified in Illinois at the end of the growing season and has increased the fire and blowing dust risk as we approach harvest. River levels have also dropped near or below low stage, increasing concerns of issues with navigation.
Working off Early August Rains
The drought peaked in early July for much of Illinois, as more active, stormy weather was present most of that month and in the first two weeks of August. Most of Illinois was 1 to 8 inches wetter than normal between mid-July and mid-August, dramatically improving soil moisture, crop conditions, and streamflow. However, drier weather has dominated since mid-August, and most of central and northern Illinois have been 1 to 4 inches drier than normal between mid-August and mid-September (Figure 1).
Figure 1. Map shows 30-day total precipitation departure from normal from mid-August to mid-September.
Soil moisture down to 20 inches has been depleted once again because of the below normal rainfall. The combination of dryness and late August heat has also sped up crop senescence and possibly affected some yields in the driest parts of the state. Meanwhile, crops in areas of the state that had been wetter in early August, such as parts of central and southern Illinois, have been relying on the remaining soil moisture.
Water table levels have also dropped across the northern two-thirds of the state as soil moisture is used. Water table levels at the State Water Survey’s WARM station in Freeport dropped more than 1 foot between August 1 and September 1 (Figure 2), and current water table depths are 1.5 feet deeper than this time last year.
Figure 2. Water table depth from the surface between August 1, 2022 and September 1, 2023 at the State Water Survey’s WARM station in Freeport.
Low River Levels Across the Midwest
Drought usually affects the flow and level of small streams and creeks first, then the tributaries of our larger rivers. When dry conditions persist for weeks to months we can see low flow along our larger rivers like the Illinois, Rock, and Kaskaskia. When those drought conditions cover most of the Midwest region, we can see low flow along the region’s largest rivers like the Mississippi and Ohio. Persistently dry conditions this summer have caused concerns of low flow conditions along the Mississippi River, like the issues we saw last fall. As of September 15, the Mississippi at Memphis was 4 feet below low stage and forecasted to approach record low values by late September. The big river hit a record low of -10.81 feet on October 21, 2022, so it is concerning that we are approaching these low values a full month ahead of last year.
The problem of big river low flow is not as easily fixed as soil moisture drought. Most rain over the next few weeks would be soaked up by the soil to replenish soil moisture and groundwater, reducing runoff to the big rivers and their tributaries. Therefore, the Midwest region will need prolonged wetter conditions over the next several weeks to help reduce or avoid the impacts of low flow on our rivers.
Where are We Headed?
The September 12 edition of the U.S. Drought Monitor has over 20% of Illinois and nearly half of the Midwest region in at least moderate drought (Figure 3). Most of the worst drought issues are in the western Midwest, while the eastern corn belt remains mostly drought-free.
Figure 3. US Drought Monitor current as of September 12.
Next week looks to be very dry across most of the region, including the Ohio Valley region that often contributes significantly to the flow of the Ohio and lower Mississippi Rivers (Figure 4). Beyond that, outlooks show the best chances of warmer conditions returning for the last full week of September, but also possibly better chances of near to wetter than normal conditions in the Midwest.
Figure 4. 7-day precipitation forecast across the Midwest for the period September 15 to September 22.
Fire and Dust Risk
We are still a few weeks from harvest in full swing, but more combines are out of the shed–and some in the field–across southern and central Illinois. Recent dry weather has quickly dried corn and beans, and combined with low humidity and dry topsoil, has increased field and grass fires across the Midwest. Extra precautions should be taken ahead of, during, and after harvest to ensure everyone stays safe considering the enhanced fire risk. You can find more information on farm fire safety here: go.illinois.edu/farmfiresafety.
Additionally, the dry crop and topsoil increase the chances of blowing dust on dry and windy days. Folks should consider weather conditions and the potential dust created when harvesting. We want to avoid dangerous blowing dust situations like what we saw this spring.
The preliminary statewide average August temperature was 73.5 degrees, 0.1 degree above the 1991–2020 average and tied for the 63rd coolest on record going back to 1895. The preliminary statewide average total August precipitation was 4.43 inches, 0.87 inches above the 1991–2020 average and the 29th wettest on record statewide.
Data are provisional and may change slightly over time.
Big August Heat, but Mild Weather Overall
The final month of climatological summer had mild temperatures overall, except for a very intense heat wave in the third week of August. Daily average temperature departures from Normal, IL show most August days were within 7 to 8 degrees of their normals, and more than half of August days were cooler than normal in the twin cities (Figure 1).
Figure 1. Daily August average temperature departures in Normal.
August average temperatures ranged from the low 70s in northern and central Illinois to the high 70s in southern Illinois, within 1 degree of normal statewide (Figure 2). Most parts of the state pushed into the mid- to upper 90s on August 24 and 25, and Chicago’s O’Hare airport recorded 100 degrees on August 24 for the first time in 11 years. The intense heat was followed by a fleeting taste of fall air, and many places saw nighttime temperatures dip into the high 40s, including 48 degrees at Marseilles. The warmest point in the state last month was Cahokia at 77.4 degrees, and the coolest point was Stockton at 69.7 degrees.
Figure 2. Maps of (left) August average temperature and (right) August average temperature departures from normal.
Overall, the preliminary statewide average August temperature was 73.5 degrees, 0.1 degrees above the 1991–2020 average and tied for the 63rd coolest on record going back to 1895.
Late Season Heat Wave
This summer will not go in the books as a particularly extreme season temperature-wise. Most parts of the state have seen near to slightly fewer than normal days with high temperatures exceeding 90 degrees, and early season drought helped nighttime low temperatures regularly drop out of the 70s. However, the largely mild weather was broken up by two intense heat waves, one in late July and the other this past month. A large upper-level ridge established over the central U.S. around August 20, bringing very warm air and high humidity from the southern U.S. and Gulf of Mexico. Daily high temperatures exceeded 95 to 100 degrees across most of the state on August 23 and 24 (Figure 3), and, combined with the humidity, pushed heat index values over 110 degrees statewide. Peoria set a new heat index record at 121 degrees, breaking its previous record from 1995.
The heat caused buckled roads in parts of central Illinois, stressed air conditioning units, and significantly increased energy demand across the Midwest. Both Champaign and Urbana schools were forced to close on August 24 due to malfunctioning HVAC systems and dangerously high temperatures inside some schools.
Figure 3. Map of high temperatures across Illinois on August 24.
Drought Relief for Some in August
July brought some better rain to parts of drought-stricken Illinois, yet moderate drought remained in more than half the state coming into August. A more active storm track last month helped bring in multiple systems that brought wetter weather to central and southern Illinois in August, helping to continue to relieve earlier drought conditions. Total August rainfall ranged from less than 2 inches in parts of northwest Illinois to over 10 inches in southeast Illinois (Figure 4). Most areas of the state south of Interstate 80 were 1 to 5 inches wetter than normal in August, while much of northern Illinois was 1 to 3 inches drier than normal.
Figure 4. Maps of (left) August total precipitation and (right) August precipitation departures from normal.
The dryness last month was most intense in northwest Illinois from the Quad Cities to the Wisconsin border. Freeport had its third driest August on record with only 0.80 inches–about 3 inches drier than normal–and the driest last month of summer since 1966. Meanwhile, Fairfield in southeast Illinois had its fourth wettest August on record with 8.11 inches.
Overall, the preliminary statewide average total August precipitation was 4.43 inches, 0.87 inches above the 1991–2020 average and the 29th wettest on record statewide.
Drought in Illinois
It’s safe to say that drought reached a peak in early July, and conditions across much of the state have improved since then. The August 29 U.S. Drought Monitor map has 16 percent of the state in at least moderate drought compared to over 50 percent on August 1 (Figure 5). The wetter weather in August helped improve crop and pasture conditions across the state, stabilize declining streams and pond levels, and promote ecological health in our natural lands. Despite the recovery, drought likely and significantly impacted crop yield potential this year, and its impact on tree health–especially in urban areas–will not be well known until next year. However, rain in July and August helped keep 2023 out of the same breath as the most severe drought years like 2012 and 1988. One exception to the wider drought improvement is in northwest Illinois, where drought conditions expanded in August. Crop impacts have been reported in this part of the state through August, and soils remain somewhat to very dry from the Quad Cities up to Rockford.
Figure 5. The U.S. Drought Monitor maps as of (left) August 1 and (right) August 29.
While drought has largely improved in Illinois, its impact to flow on the Midwest’s largest rivers remains. Dry conditions in the Upper Mississippi and Ohio Basins have led to concerns of low flow and navigation and ecology impacts along the Mississippi River. Forecasts indicate the Mississippi River at Memphis is likely to reach low stage in early September (Figure 6). Dry soils across the larger Midwest region will likely slow river stage recovery from any additional rain in early fall. Therefore, without a significant shift to wetter conditions and/or an errant tropical system moving into the region, low flow issues on the Ohio and Mississippi Rivers are likely to continue or intensify into September.
Figure 6. Plot shows current and forecasted levels on the Mississippi River at Memphis.
Summer in Illinois
Climatological summer encompasses June, July, and August, and the season often brings more than its fair share of intense weather. This past season was on the mild side, temperature-wise, and was somewhat to much drier than normal. The abundance of gray in the maps in Figure 7 indicates average temperatures in all three summer months were mostly within 1 degree of normal across the state. While the Midwest was exposed to ephemeral heat in July and August, persistent extreme high temperatures stayed well south, making for one of the hottest summers on record in parts of Texas and New Mexico.
Figure 7. Maps show average temperature departures for June, July, August, and climatological summer.
The summer season began with a very dry June that kicked off drought concerns across the state. Wetter conditions in July and August helped reduce or eliminate drought in central and southern Illinois, but parts of northern Illinois remained dry in the latter part of the season. Summer precipitation totals ranged from 6 inches in parts of northwest Illinois to over 20 inches in parts of southeast Illinois. Most of the northwest part of the state was 4 to 8 inches drier than normal in summer, while much of southern Illinois was 2 to 10 inches wetter than normal (Figure 8).
This past season was the 13th driest summer on record in Moline with 6.89 inches, and the driest since 2012. It was also the 20th driest summer on record in Rockford with 7.63 inches, which is less than half of the summer total from last year. Three of the past four years have seen top 20 driest summers in Rockford. In contrast, this summer was one of the wettest in far southern Illinois, and it was the fifth wettest on record in Paducah, Kentucky with 18.90 inches.
Figure 8. Maps show (left) summer total precipitation and (right) summer precipitation departure from normal.
Overall, the preliminary statewide average summer temperature was 73.4 degrees, 0.4 degrees below the 1991–2020 average and tied for the 57th coolest on record going back to 1895. The preliminary statewide average total summer precipitation was 11.51 inches, 0.76 inches below the 1991–2020 average and the 69th driest on record statewide.
Outlooks
September brings in what is undoubtedly the best season in Illinois. However, outlooks for the month of September suggest we may need to wait a bit for more consistent fall weather, with higher odds of warmer and drier than normal weather for the first month of the season (Figure 9a). Meanwhile, guidance for climatological fall is less than confident, with equal chances of warmer, cooler, wetter, and drier than normal weather.
Figure 9. Maps show (left) temperature and (right) precipitation outlooks for the month of September and the fall season (September-November).
The preliminary statewide average October temperature was 53.1 degrees, 1.6 degrees below the 1991–2020 average and tied for the 40th coolest on record going back to 1895. The preliminary statewide average total October precipitation was 2.30 inches, 0.61 inches below the 1991–2020 average and tied for 52nd driest on record statewide.
Data are provisional and may change slightly over time.
Mild October Temperatures
October 2021 was the fifth warmest on record in Illinois. The unusually warm and rainy weather last year put a damper on both harvest and fall festivities. October this year though did not disappoint fall lovers. October followed September’s lead and brought mostly mild temperatures across the state. As the temperature departures from Aurora in Figure 1 show, 16 of the first 21 days in October were cooler than normal, and many were 5 to 15 degrees below normal. Only the third week of the month had temperatures more than 10 degrees above normal. Average October high temperatures ranged from the low to high 60s, with lows in the 40s and low 50s. The result was very pleasant weather across the entire month, which, along with dry conditions, permitted a relatively quick harvest and plentiful opportunities to enjoy fall festivities.
Figure 1. Daily October average temperature departures in Aurora.
Cool October nights brought regular frost across the state, and an earlier than normal first fall freeze. For example, Du Quoin recorded its first fall 32-degree freeze on October 9, about 10 days earlier than the 1991–2020 average. Most places saw nighttime temperatures dip below the hard freeze mark of 28 degrees later in the month, including a 20-degree low in Monmouth and a 22-degree low in Carbondale.
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 in the state was Elizabeth in Jo Daviess County with an average October temperature of 49.2 degrees.
Figure 2. Maps of (left) October average temperature and (right) October average temperature departures from normal.
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 also broken at 17 stations. Cairo tied its all-time October low minimum temperature record with a 25-degree low on October 19.
Overall, the preliminary statewide average October temperature was 53.1 degrees, 1.6 degrees below the 1991–2020 average and tied for the 40th coolest on record going back to 1895.
Continued Dryness Causes Issues
September was drier than normal in most places around the state, and the dryness persisted into the first two-thirds of October (Figure 3). Most areas picked up less than 1 inch of total precipitation between October 1 and 21, 1 to 3 inches less than normal over the time period.
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 has contributed to higher transportation costs and grain storage issues.
Figure 3. Maps show (left) total precipitation and (right) precipitation departure from normal between October 1 and 21.
The last week of the month brought wetter weather statewide, including a few places that picked up 3 to 4 inches in a single week. October total precipitation ranged from over 4 inches in southwest Illinois to less than 1.5 inches in far northwest Illinois (Figure 4). 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 last month.
Overall, the preliminary statewide average total October precipitation was 2.30 inches, 0.61 inches below the 1991–2020 average and tied for 52nd driest on record statewide.
Figure 4. Maps show (left) October total precipitation and (right) October precipitation departure from normal
Outlooks
Climate Prediction Center outlooks for November mostly point to equal chances of warmer/cooler and wetter/drier than normal conditions (Figure 5). However, as we continue into our third consecutive La Niña cool season, outlooks are increasingly taking a very La Niña-esque appearance. Namely, much of Illinois is leaning toward wetter than normal conditions from December through February (Figure 6). A wetter winter would be beneficial in reducing the soil moisture deficits and improving streamflow as we move into spring.
Figure 5. Maps show (left) temperature and (right) precipitation outlooks for November.Figure 6. Climate Prediction Center (left) temperature and (right) precipitation outlooks for December through February.
