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The preliminary statewide average December temperature was 33.4 degrees, 1.8 degrees below the 1991–2020 average and tied for 36^th warmest on record going back to 1895. The preliminary statewide average total December precipitation was 2.90 inches, 0.47 inches above the 1991–2020 average and tied for 31^st wettest on record statewide.    

Data are provisional and may change slightly over time.

Roller Coaster Temperatures

Day to day temperature variability in Illinois is highest in climatological winter, and December followed suit with regular dips and jumps in daily temperature, as shown in Figure 1 from Aurora. Daily average temperatures were 10 to 20 degrees below normal in the first week of the month, were 15 to 25 degrees above normal in the final week of the month, and jumped around in between (Figure 1).

When taken altogether, December average temperatures ranged from high 20s in northern Illinois to the low 40s in southern Illinois, between 1 and 5 degrees above normal (Figure 2). The warmest place in the state last month was Olmstead in Pulaski County with an average December temperature of 41.4 degrees. The coolest place in the state was Stockton in Jo Daviess County with an average December temperature of 26.6 degrees.  

The milder days last month broke 3 daily high maximum temperature records and 54 daily high minimum temperature records. Meanwhile the cooler days in December broke 23 daily low maximum temperature records and 6 daily low minimum temperature records in Illinois.

Overall, the preliminary statewide average December temperature was 33.4 degrees, 1.8 degrees below the 1991–2020 average and tied for 36^th warmest on record going back to 1895.

Wetter December with Some Snow, I Guess

December wasn’t a washout anywhere but brought enough precipitation to continue improving water conditions from peak fall drought. December total precipitation ranged from over 6 inches in far southern Illinois to around 1.5 inches in northern Illinois. Most areas of the state south of Interstate 64 were 1 to 3 inches wetter than normal last month, while parts of northern Illinois were around 1 inch drier than normal (Figure 3).

The wettest part of the state was, again, Olmstead in Pulaski County, which picked up just over 10 inches in the final month of the year. The driest place in the state in December was Freeport, with only 0.89 inches for the month. Overall, the preliminary statewide average total December precipitation was 2.90 inches, 0.47 inches above the 1991–2020 average and tied for 31^st wettest on record statewide.   

As is often the case in milder Decembers, snowfall was a little harder to come by across Illinois last month. December total snowfall ranged from around 5 inches in far northern Illinois to less than a tenth of an inch in far southern Illinois, between 1 and 6 inches below normal (Figure 4). Snowfall so far this season has also been below normal across Illinois, to the tune of 1 to 10 inches.

Outlooks

Climate Prediction Center outlooks for January show an extension of colder than normal conditions from the northern Plains into much of the Midwest and Southeast US. January Outlooks show mostly equal chances of above and below normal precipitation for the first month of 2025 (Figure 5).

Meanwhile, 3-month outlooks for January through March show equal chances of warmer and cooler than normal conditions but paint a decidedly wetter than normal pattern across Illinois (Figure 6).

The preliminary statewide average November temperature was 46.6 degrees, 4.4 degrees above the 1991-2020 average and tied for the 10^th warmest on record going back to 1895. The preliminary statewide average total November precipitation was 4.15 inches, 1.07 above the 1991-2020 average and the 20^th wettest on record statewide.

Data are provisional and may change slightly over time.

Mild November with a Chilly End

November can be a challenging month for those yearning for summer to come back. However, as daily average temperature departures in Jacksonville show, the past month brought mostly mild temperatures that felt more like early fall than early winter (Figure 1). Several days in the first and third weeks of the month were 10 to 20 degrees warmer than normal. Thanksgiving week brought a big temperature change on the back of a strong cold front. The last few days of the month saw temperatures that that were 5 to 15 degrees below normal, including several nighttime low temperatures in the teens.

November temperatures ranged from the low 40s in northern Illinois to the mid-50s in southern Illinois, around 2 to 7 degrees above normal (Figure 2). Several places saw high temperatures into the high 70s in early to mid-November, including 79 degrees in Decatur and Marseilles. Meanwhile, the last week of the month brought some very low temperatures, including 7 degrees in Stockton and 9 degrees in DeKalb. The coldest point in the state last month was Stockton at 41.2 degrees, and the warmest point was Du Quoin at 53.3 degrees.

Much November Rain for Which to Be Thankful

September and October were both very dry months across Illinois, outside of the few places that saw rain from the remnants of hurricane Helene. November flipped that script and brought quite a bit of rain across much of the state. November totals ranged from over 8 inches in the St. Louis Metro East area to around 3 inches in north-central Illinois. Parts of southwest and central Illinois were 5 to 8 inches wetter than normal last month, while much of far southern Illinois was 1 to 2 inches drier than normal (Figure 3). Some of the more impressive November totals include 9.97 inches in Granite City and 8.38 inches in Cahokia Heights. Meanwhile, Moline and Rockford only picked up around 2 inches total for the month. Last month was the wettest November on record in Edwardsville with 9.97 inches, and it was the first November since 1946 with over 9 inches of rain in Edwardsville.

Overall, the preliminary statewide average total November precipitation was 4.15 inches, 1.07 above below the 1991-2020 average and the 20^th wettest on record statewide.

Some Snow, At Least

Snowfall in November is not a rare occurrence, but certainly is not a mainstay in Illinois. This year, the northeast corner of the state was the big “winner” for pre-Thanksgiving snowfall, with lake-enhanced snow contributing to widespread 1.5 to 3 inch totals across the Chicagoland area last month. The Interstate 64 corridor also picked up between a quarter and half an inch of snow in the final week of November (Figure 4). Otherwise, the three months comprising climatological fall (September through November) were snow free. Fall snowfall deficits ranged from near 3 inches below normal in northwest Illinois to less than half an inch below normal in the St. Louis Metro East area (Figure 4).

A Mild Fall in Illinois

Climatological fall includes September, October, and November, and — for my money — it is the best weather season Illinois has to offer. This past season’s average temperatures ranged from the mid-50s in northern Illinois to the low 60s in southern Illinois, between 2 and 5 degrees above normal (Figure 5). It was a top 10 warmest fall on record in most parts of the state, including the third warmest fall on record in Chicago, the fourth warmest on record in Peoria, and the fifth warmest on record in Champaign-Urbana. Champaign had only nine nights with minimum temperatures below freezing, which was the fewest since 1973 and the fourth fewest on record.

Overall, the preliminary statewide average temperature in fall was 57.9 degrees, 3.3 degrees above the 1991-2020 normal and the fourth warmest fall on record in Illinois.

Fall season total precipitation ranged from over 15 inches in southwest Illinois to less than 4 inches in parts of north-central Illinois. Only the southwest part of the state was wetter than normal, while the rest of the state was 1 to 6 inches drier than normal this fall (Figure 6). It was a top 10 driest fall on record in Freeport (4.47 inches), Moline (3.77 inches), and Galesburg (4.52 inches).

Overall, the preliminary statewide fall total precipitation was 7.88 inches, 1.81 inches below the 1991-2020 normal and the 48^th driest fall on record in Illinois. It was also the fifth consecutive drier-than-normal fall in Illinois.

Outlooks

Welcome to winter! December brings in the coldest, snowiest season of the year. Climate Prediction Center outlooks for the month of December don’t show any strong signals for Illinois, with equal chances of a warmer, colder, drier, and wetter than normal end to 2024 (Figure 7a). Outlooks for climatological winter (December through February) are a bit more telling, with better chances of wetter than normal winter weather (Figure 7b).

The preliminary statewide average October temperature was 58.6 degrees, 3.8 degrees above the 1991-2020 average and tied for 14^th warmest on record going back to 1895. The preliminary statewide total October precipitation was 0.96 inches, 2.30 inches below the 1991-2020 average and the 10^th driest on record.  

Data are provisional and may change slightly over time.

Mild October Temperatures

October is the most quintessential fall month, weather-wise, as we transition from a more summer-like September to what is often a more winter-like November. This year, however, October temperatures were more akin to the first part of the season than the last part. Temperature departures from normal in Rockford show that while autumn cool air visited us last month, it was fleeting. More days in October had temperatures that were 5 to 10 degrees above normal, and a few days had average temperatures that were 20 to 30 degrees above normal across the state.

October average temperatures ranged from the mid-50s in northern Illinois to the low 60s in southern Illinois, between 2 and 5 degrees above normal (Figure 2). High temperatures reached into the 80s well into the final week of the month, including the third latest 80-plus-degree high temperature on record in Rockford (Oct. 29). However, low humidity also helped nighttime temperatures dip into the 20s and 30s on many nights, including 20 degrees in Joliet and 24 in Monmouth. The coolest point in the state last month was Stockton in Jo Daviess County at 54.6 degrees, and the warmest point was Olmstead in Pulaski County at 63.5 degrees. Last month was a top 15 warmest October on record in many parts of the state and was the ninth warmest October on record in Chicago.

Overall, the preliminary statewide average October temperature was 58.6 degrees, 3.8 degrees above the 1991-2020 average and tied for 14^th warmest on record going back to 1895.

Drier Than the Numbers Imply

October can be an important month for precipitation in Illinois. Not only does the month start the new water year, but October is when we begin the slow climb out of the hydrologically driest time of the year, between July and September. At the same time, an excessively wet October can spell trouble for the timely harvest of grain and specialty crops.

Most of last month was somewhat to extremely dry across Illinois. In fact, many parts of northern and central Illinois had less than a quarter of an inch of precipitation into the final week of the month. Freeport had 30 consecutive days with no measurable precipitation, the fourth longest dry streak in the city’s more than 100 year record. The dry weather desiccated soils and dropped flow on many rivers and their tributaries, including along the Mississippi and Illinois rivers. A third straight very dry fall season continued to challenge pasture conditions around the state and increased the risk of fire and blowing dust. Large field fires burned hundreds of acres of farmland in north central and northeast Illinois the final week of the month. The U.S. Drought Monitor expanded moderate to severe drought across northern and central Illinois in response. The dry weather accelerated harvest across Illinois. As of Oct. 27, the U.S. Department of Agriculture estimated nearly 90% of both corn and soybeans were harvested in Illinois, well ahead of the five-year averages by that time.

A strong low pressure system moved across the region in the final couple of days in October, bringing more significant rainfall to the state. Total October precipitation ranged from less than a quarter of an inch in east central Illinois to over 3 inches in northwest Illinois. Only the Quad Cities and surrounding areas were near normal for October precipitation, while most of the rest of the state was 1 to 4 inches drier than normal last month (Figure 3). 

The preliminary statewide total October precipitation was 0.96 inches, 2.30 inches below the 1991-2020 average and the 10^th driest on record. 

Outlooks

November is truly a transition month as the days become shorter and the temperatures cooler. It is also the month where we begin to see those typically Illinois winter weather days with hours upon hours of thick clouds that produce no more than five raindrops or flakes. Chili weather, pure and simple.

That said, the Climate Prediction Center shows higher odds of warmer than normal weather in November (Figure 4). The same outlooks have best chances of above average precipitation, too. However, it’s important to note that many places will likely see nearly their entire average November precipitation in just the first week of the month. So the Climate Prediction Center is hedging their bets, so to speak. 

Extremely dry conditions this fall have pushed the northern half 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

The remnants of Hurricane Helene mostly relieved drought conditions in southern Illinois in late September. However, following the laws of conservation, drought migrated to northern Illinois. Precipitation has been very hard to come by since the start of September in much of northern Illinois. Several places, including Dubuque and Freeport, have had a top 5 driest start to the fall on record. Freeport, specifically, has gone 23 consecutive days with no rainfall. Much of the northern half of the state has had less than 50% of normal precipitation since mid-September, and a few spots have had less than 10% of normal (Figure 1).

Figure 1. Precipitation over the last 30-days ending on October 17th, expressed as a percent of normal.

The U.S. Drought Monitor has greatly expanded moderate and severe drought in northern and central Illinois in response to the recent dryness. Roughly 40% of the state is in at least moderate drought (Figure 2).

Drought Impacts

Agricultural impacts from our current drought situation include deteriorating pasture conditions and problematically low grain moisture levels as harvest continues. The dryness does help progress a 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 Illinois River is approaching near record low levels in several places including Marseilles. The Mississippi River has returned to low levels after a bump from Helene. Tower Rock on the River is now walkable from the Missouri side.

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

The next 7-days will remain dry across Illinois; however, there are some signs of some moisture return in to the Midwest as we move into the final week of October (Figure 3). At least some rain would be beneficial to tamping down dust and fire risk and maybe steadying some river levels.

Figure 3. Week 2 precipitation outlook for October 25-31 from the Climate Prediction Center: https://www.cpc.ncep.noaa.gov/.