Many rivers were still in flood as a dome of cooler/drier Canadian-source high pressure moved into the Chicago area Monday – temperatures and dew-points were some 15-degrees cooler/lower than Sunday with highs in the middle 70s and dew-points in the upper 50s. Tuesday will find us still under the influence of the now-departing high pressure with southerly winds boosting temperatures back into the 80s and a little more humidity creeping back into the air. An on-shore easterly wind will again hold temperatures in the 70s at the lakefront.
Wednesday a cold front will approach from the northwest with southwest winds directing the return of much warmer and more humid conditions. Strong to severe thunderstorms with potentially damaging winds, large hail and flood-producing downpours look probable beginning in westernmost sections in the late-afternoon/evening and spreading over northeast Illinois into northwest Indiana Wednesday night.