Late Sunday afternoon, thunderstorms suddenly developed in portions of Will, DuPage, Kane, Cook, McHenry and Lake counties as an easterly lake breeze off Lake Michigan collided with moist southerly inland winds and a weak warm front over northeast Illinois. National Weather Service radar indicated some moderate rainfall in a few spots, but for the most part just thunder and brief light rain were observed. Severe thunderstorm warnings were issued, and a power outage occurred in the Naperville area.
The Illinois EPA issued an Air Pollution Action Day alert for Chicago today. It appears that the heat will continue into Thursday, which could make the last seven days in June the second-hottest June 24-30 on record at Chicago.
This is the season of infrequent frontal passages and a reliance on spotty thunderstorms for most rainfall—a bad omen as all indicators point toward the present moderate to severe drought over northern Illinois intensifying.

Light east winds may provide some relief from the heat along the Lake Michigan shoreline Sunday, while inland another hot humid day is expected. If readings reach 90° at Midway and O’Hare today, it will mark four straight days with 90° or higher at both sites and raise the total number of 90° days this June to five at O’Hare and ten at Midway. With a southerly flow forecast to continue into mid-week, June 2005 may well end on a string of eight consecutive 90° days—an event that has never occurred at either Midway or O’Hare. Midway holds the end-of-June record set back in 1931 when each of the last 7 days of June that year hit 90°.
Hot and humid conditions will continue the next few days, but any showers will be few and far between. Even the passage of a cold front Thursday may trigger another opportunity for rain, but the nature of showers/thunderstorms being mostly brief and “hit or miss” will have a negligible effect on the strengthening drought.

Heat has hit early and comparatively hard this year, a development which has often signaled enhanced prospects for more than the usual number of 90° days. Eight comparably hot years since 1928 have gone on to produce an average of 39 days of 90s—far more than the typical 24 which normally occur in the city.
While O’Hare Airport’s 96° high Friday missed the record by only a degree, the 98° high at Midway Airport brings to eight the number of 90s on the books in 2005. Friday’s scorcher was the hottest weather Chicagoans have experienced in three years. Only 176 days over the past 77 years have been as hot or hotter.
The area’s hottest readings on Friday included 98° at Wheeling, 99° at Kankakee and 100° at Remington, Ind.
The string of 90° highs predicted each day through Thursday would make this the first time since 1931 that the final week of June has produced 90s each day.