ROCKFORD (WREX) — The Rockford region's first 90° day is possible Tuesday ahead of an approaching cold front. Building heat and humidity could lead to strong storms into midweek.
On average, Rockford observes the first 90°+ temperature on June 5th. Some areas of the Stateline may not crack the 90° mark, but it does look like Rockford is going to see the first one of 2020. Tuesday is going to be a pool day if you are lucky enough to have access to one, especially since heat index values are going to climb into the middle 90s.
Clear skies early Tuesday evening gradually lead to an increase in cloud cover later and storm chances. Storms should begin to fire late Tuesday across the Upper Midwest, with the congealed thunderstorm complex aiming at southern Wisconsin during the overnight hours. Most of this bypasses the Stateline to the north, but a small threat for severe weather remains along and north of I-88.
A marginal risk, or a 1 on a 1-to-5 scale, of severe weather is possible during the predawn hours of Wednesday. Large hail and damaging winds are the primary threats with early Wednesday's activity.
Severe threat pushes south:
As stronger storms push south early Wednesday, they'll bring areas of central Illinois the threat for severe weather. By shortly after sunrise Wednesday, most areas north of I-80 are going to clear out from the threat for strong storms.
A gradual decrease in cloud cover is likely by Wednesday afternoon as a more stable air mass settles overhead. High temperatures in the middle 80s are going to feel cooler than the lower 90s Tuesday afternoon.
Quiet weather persists into Thursday, with highs topping out in the middle 80s. A return to isolated thunderstorm chances by Friday as highs remain nearly steady.