Which month features the largest spread in high, low temperatures?

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Dear Tom,
Comparing Chicago record high and low temperatures, which month features the largest spread? March seems like a good bet.
— Tom Gregg, Niles

Dear Tom,
March it is. March leads all other months with an incredible 100-degree span between its highest and lowest temperatures, from 88 on March 29, 1986, to 12 below zero on March 4, 1873. Runner-up months are February and December, each with a 96-degree spread between extremes.

Chicago experiences a continental climate, the main characteristic of which is large, abrupt and frequent temperature fluctuations. While wide-ranging extremes most often occur in winter and spring, September is no stranger to huge temperature shifts. It’s been as hot as 101 degrees on Sept. 1 and 2, 1953, and as cold as 29 on Sept. 28, 1942; Sept. 30, 1984; and Sept 23, 1995, a range of 72 degrees