

Chicago's warmest and coldest January days

January 30, 2006|By Tom Skilling

There is an almost 100-degree difference (94 degrees to be exact) between Chicago's warmest temperature in January 56 years ago and the month's coldest temperature just 21 years ago. It shows vividly the huge variations that occur in a continental climate like the one experienced in northern Illinois.

THE COLDEST: JAN. 20, 1985

With a northerly jet stream providing a quick, smooth ride south, the huge arctic-origin high pressure center flowed south through central Canada into the northern and central Plains. The coldest sections of the high extended from the Dakotas into central Illinois with readings that morning in the mid to upper -20s. Clear nighttime skies and a fresh snow cover along with light winds allowed maximal radiational cooling.

THE WARMEST: JAN. 25, 1950

On the backside of a retreating (to the east) high pressure system that pulled air all the way from the warm southwestern United States into northeast Illinois, Chicago was just on the cusp of the warm air tongue, which was led by a warm front along the Illinois-Wisconsin border. A cold front was bearing down on the area from the west. Falling pressure and increased winds just ahead of the cold front enhanced warming. Rockford sat just north of the warm front, and the cold front moved through before the warm air arrived--Rockford's high temperature was 40(degrees) while locations to the east experienced readings in the 60s.

Sources: National Weather Service, Frank Wachowski

WGN-TV/Paul Dailey


