No other month sees normal temperatures decline at a faster rate than occurs in November here. The steady seasonal retreat in temps shaves 16-degrees off Chicago's normal daily high between the first and the 30th of the month. Daytime highs will retreat from 56-degrees as November opens to 40 by month's end.
The sunlight we receive is weaker this time of year, arriving at a lower angle as the sun treks farther and farther south across the sky. That plus the reduction in the amount of sunlight we receive each day drives the seasonal cooling.
Morning temps the coolest here in 8 months; a second chilly night ahead
Early-risers Thursday morning experienced the coolest temperatures since last March with 20s at many locations, particularly away from Lake Michigan.
Not since last March have official nighttime lows here dipped into the 20s.
October 2012 the 31st coolest in 142 years; the second consecutive month to post below normal temps
The books closed on October 2012 at midnight last night. The month was a cool one---ranking 31st chilliest among the 142 Octobers over Chicago's observational record. It was the second consecutive month to post a temperature deficit.
October 2012 finished a degree and a half below the long term average at O'Hare and more than 3 degrees cooler than October a year ago.
A record breaking 13 consecutive months have posted greater than normal sunshine
It may have been a cool month, but October also managed more sunshine than is typical this time of year. The month saw 59 percent of its possible sunshine---more than the 57 percent considered normal.