This autumn has not only been characterized by warm daytime temperatures, but by exceptionally mild nights as well. Before Sunday morning’s frosty lows, the city’s lowest official minimum temperature this fall had been just 39º and that was recorded more than a month ago on Sept. 15. Frost had been limited to some scattered occurrences at far inland locations.
All that is changing this week, as two more intrusions of cold air will bring some of the season’s lowest daytime readings, and frosty overnight lows as well. Some frost will be possible again Sunday night away from the heat of the city.
However, sandwiched between the cold snaps, a midweek warm-up will boost the mercury back into the 60s on Tuesday and Wednesday, raising prospects for another mild Halloween—a frequent occurrence here in recent years. Ten of the last 12 Halloweens have been warmer than normal.
--By Tom Skilling, WGN-TV Chief Meteorologist
WGN-TV Chief Meteorologist Tom Skilling and the WGN Weather Center staff provide daily coverage of weather in the Chicago area.
