When does the lake start freezing in the Chicago area?
— Amit Jhingran, Chicago
The onset of ice formation in the Chicago area on extreme southern Lake Michigan is highly variable and dependent on the severity of the winter season. When an early-season cold wave delivers a prolonged period of sub-freezing temperatures, ice formation can begin as early as mid-December, but in more typical winters, it may not begin to form until late January or early February.
In the mildest winters or winters where temperatures frequently fluctuate from below to above freezing, ice may not form at all. Checking the last 10 winters, the earliest that ice has formed was in mid-December 2013, when temperatures remained well below freezing from Dec. 6-16 during a cold snap that included three days when the mercury plunged to zero or below.