The heat grew oppressive—even dangerous—Monday. No single summer day in the seven years since 1999 has generated a more stifling temperature/humidity combination. Mid-afternoon thermometer readings of 95° combined with stifling Amazon Valley-level 76° dew points—a level higher than at most weather reporting stations on the Gulf of Mexico—to produce a 109° heat index at O’Hare and 108° at Midway. At Northerly Island, where the dew point hit 80°, the heat index soared to 114°.
Had all that moisture been uniformly squeezed from the air Monday, more than 2" of rain would have fallen across the area. Late evening t-storms, some 12-miles tall, produced damage and power outages in Rockford amid their dazzling lightning displays. More than 3,200 cloud to ground strokes occurred in one 10 minute period late Monday within a 225 mile radius of Chicago.
-Tom Skilling
WGN-TV Chief Meteorologist Tom Skilling and the WGN Weather Center staff provide daily coverage of weather in the Chicago area.
