Midway airport topped out at 91° Monday, with O’Hare reaching 89°, both the highest readings of the year thus far. The developing heat now spreads far and wide, from the mid Atlantic to the Rockies. Temperatures in the 90’s in Chicago during the first 10 days of June are not that unusual, occurring about half the time (53 percent), but a string of three or more days are unusual this early in the summer.
Some relief will be moving east into the high Plains over the next few days, but warm, humid conditions are expected over northern Illinois right through the weekend. Changes in the upper pattern now project the weak jet stream, the delineator between warm and cool air, will settle well north off Chicago, with an associated cold front sinking only as far south as the Wisconsin line late in the week. This heat and humidity in an unstable environment adds up to a chance for t- storms and much needed rain almost every day, with the best chance on Thursday.

Sunday saw temperatures creep higher around Chicago, peaking at 90° at Midway Airport—the first such reading of the year. Although O’Hare Airport topped out at 87° for Chicago’s official high temperature, it was also its warmest of the year. Hotter temps included 94° at Champaign and 95° at Goshen, Ind. Chicago also escaped a second day of severe weather, as most occurred south or east of the city—including reports of two tornadoes.
Cooler, less humid air sweeps in Monday as west winds trail the exiting heat and humidity to the east. After two warm but less humid days, this front inches back northward and stalls over the Chicago area from Wednesday into the weekend. This system will act as a focus for upcoming thunderstorms, possible from Wednesday through Saturday, with the best chance of needed rain late in that period.