As January wraps up, we can put some numbers on how cold it was. The statewide average temperature for January was 18.2 degrees, which is 8.1 degrees below normal, and it made this month the eighth-coldest in 120 years of statewide record keeping. The numbers come from state climatologist Jim Angel, who says the cold wasn’t unprecedented; it was just a persistently cold month.
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“While we’ve had some very cold temperatures, they weren’t necessarily record-breaking. We had a couple of highs and low temperatures for a particular day, especially on Jan. 6, that may have set the record (lowest) high and low for that date, but we really didn’t set anything like coldest temperature ever at a particular site,” he said. The average temperature for the month is determined by taking the average of the daily high temperatures and the average of the daily low temperatures, and determining the mean between the two.
The coldest January on record in Illinois was 1977, with an average of 10.3 degrees.