The preliminary statewide average October temperature was 58.6 degrees, 3.8 degrees above the 1991-2020 average and tied for 14th 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 10th 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 14th 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 10th 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.
