A HEAT ADVISORY will go into effect for Stephenson, Jo Daviess, Carroll and Whiteside counties beginning Noon Saturday following the passage of a warm front. Behind the front, temperatures are expected to climb into the low 90s, but with a rising dew point temperature (low to mid 70s) it could feel more like the 100-105 degrees.
While the high heat and humidity are likely for some Saturday, it’s also possible that not everyone will experience the hot and humid conditions. Thunderstorms are expected to develop in Iowa late Friday night, moving into northern Illinois between 11pm and 2am. Some of those storms could continue into Saturday morning, slowing the progression of the warm front north. If that occurs it is possible that some areas across north-central Illinois and south-central Wisconsin don’t get as hot due to leftover showers and cloud cover. This is why the advisory has not been issued for the entire region.
If the storms Saturday morning are quick to move out, along with the cloud cover, then the warm front will quickly lift north into southern Wisconsin by the afternoon. This would mean temperatures rising into the low to mid 90s, along with heat index values over 100 degrees, would be more common throughout the day. Right now the forecast high for Saturday is 91 degrees, but it is possible that some areas may be slightly cooler/less humid than that, depending on morning storms and cloud cover.