Illinois weather was cold and dry in November

[December 16, 2019]    November temperatures were well below the long-term average across the state, breaking hundreds of local daily records, according to Illinois State Climatologist Trent Ford at the University of Illinois’ Illinois State Water Survey.

The preliminary statewide average temperature for November was 35.6 degrees, about 7 degrees below Illinois’ 30-year normal and tied for the ninth coldest on record.

The intense cold weather at the end of October continued into the first two-thirds of November. Average temperatures ranged 10 to 15 degrees below normal for the first half of the month.

Between Nov. 1 and Nov. 15, 149 daily low maximum temperature records and 177 daily low minimum temperature records were broken across the state. Several all-time November temperature records were broken as well, including both the all-time November low minimum and low maximum temperature records in Robinson, Illinois, in Crawford County.

At Chicago’s O’Hare airport, 22 out of 30 November days experienced an average temperature below the long-term mean, including the first 19 days of the month. Stations in Knox, Jo Daviess, Carroll, and Whiteside Counties observed daily minimum temperatures below 0 in November, the lowest being -4 degrees in Altona in Knox County on November 7.

A shift in the upper-atmosphere trough around November 20 allowed temperatures to moderate. Average temperatures between November 16 and November 30 were between 1 and 3 degrees below normal across the state.

Preliminary data suggest November was drier than average for most of the state. The statewide average November precipitation total was 2.51 inches, approximately 0.96 inches below the 30-year normal.

November precipitation was below the long-term mean for all of Illinois north of Interstate 64. Monthly precipitation totals ranged from 1 to 2 inches in central and northern Illinois to over 6 inches in far southern Illinois. These totals represented between 2 inches below and 2 inches above normal.

Despite the overall dryness, abundant October precipitation and timely rain and snow throughout November alleviated all abnormally dry conditions across the state. According to the U.S. Drought Monitor, the entire state has been free of drought and abnormally dry conditions since November 5.

Although total precipitation was below normal for most of the state this last month, snowfall totals were well above average. Total November snowfall accumulations ranged from nearly 12 inches in northern Illinois to just over half an inch in far southern Illinois. Accumulations were between 1 and 6 inches below the long-term November average snowfall totals.

Measurable snowfall with an accumulation greater than 0.10 inches occurred in November as far south as Cairo in Alexander County. The highest November snowfall total was 11.7 inches in McHenry County.

Just as impressive as the snowfall totals this month was the number of days with measurable snowfall. The long-term weather station in Freeport recorded five days in November with measurable snowfall, tied for the second most since 1948 and the most since 1978.

Both short-term 8- to 14-day outlooks and 1-month December outlooks from the Climate Prediction center show strongly elevated odds of above normal temperatures across the state. The shorter and longer outlooks show slightly elevated odds of above normal precipitation, although odds are weaker than for temperature outlooks. Winter (December–February) outlooks show an equal chance for temperature and slightly elevated odds for above normal winter precipitation.

[Lisa Sheppard]