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Dear Tom,

What are the historical coldest and warmest times of the year, after which temperatures begin to increase or decrease?

Joe Posewick New Lenox

Dear Joe,

Chicago’s normal daily temperatures have been on a slow, but steady decline since they peaked with a high of 85 and a low of 67 during the period of July 11-24. That decline will end after the annual temperature cycle bottoms out with a normal high of 31 and a low of 18 during the January 16-28 period, after which readings will again begin to slowly rise.
   It is interesting to note that both the city’s warmest and coldest times of the year come three to four weeks after the solstices as the Earth continues to gain heat in summer and lose heat in winter following the solstices, days with the longest and shortest daylight, in what is known as the “lag of the seasons.”