Freeze Warning for most of the Chicago area 11PM CDT Saturday until 9AM CDT Sunday
A heavy frost with freezing temperatures is expected over most of the Chicago area later Saturday night into Sunday morning . Temperatures should drop into the mid and upper 20s away from Chicago with lowest readings along and west of the Fox River Valley. Temperatures in the city of Chicago will likely range from near 30-degrees on the outlying areas to the middle 30s in the Loop and along the immediate Lake Michigan shoreline. The Freeze Warning will extend farther south and west across Illinois as far south as the Texas Panhandle and north into Wisconsin (see dark-blue/purple-shaded areas on the highlighted map above and the larger-area map below).
The deep center of low pressure will slowly move northeast away from Wisconsin into the Canadian province of Ontario in the next 24 to 36-hours. As this complex low pressure system slowly departs to the northeast, west to northwest winds will gradually diminish here and clouds finally thin and break up after midnight Saturday night. With the loss of cloud cover and lighter winds, maximum radiational heat loss will occur, allowing temperatures to fall into the 20s away from the city with a hard freeze expected.
Clouds could persist in northwest Indiana a little longer, possibly modifying or delaying the temperature loss there.