Chicago and Milwaukee hit 103°; relief coming by Sunday

It was another day of triple-digit heat across the Midwest Thursday, as the nation continued to bake in the intense heat of the record-breaking summer of 2012. Chicago hit 103° on Thursday, just 2° below the city's all-time hottest temperature of 105°, set on July 24, 1934. The Windy City might have exceeded their all-time heat record, but for the fortuitous formation of a small but intense thunderstorm that hit the airport at 2:45 pm. The storm brought a wind gust of 52 mph to the airport and cooled the temperature by 20°. A wind gust of 92 mph was recorded 4 miles offshore over Lake Michigan. Thursday was the hottest day in Chicago since a 104° reading on July 13, 1995. Milwaukee, WI also hit 103° Thursday, which tied for the 3rd hottest temperature in city history. Madison's 104° was their hottest day since 1988, and also tied for the 3rd warmest temperature ever measured in the city. Madison's all-time high is 107°, set July 14, 1936. St. Louis hit 105°, the eighth consecutive day the city has hit triple digits. This streak is now the 3rd longest such streak in city history; the only longer streaks occurred during the Dust Bowl summer of 1936 (streaks of 13 and 9 days.) The current forecast for St. Louis calls for highs of 107 - 108° Friday and Saturday, which will likely bring the city's streak of 100°+ days to ten by week's end. St. Louis' all-time hottest temperature is 115°, set in 1954.


Figure 1. The severe weather map for Friday, July 6, 2012, showed that advisories for extreme heat (pink colors) were posted for portions of 25 states.

The forecast: record heat Friday and Saturday, then relief
More record-breaking triple-digit heat is expected Friday and Saturday across much of the Midwest and Tennessee Valley, but a cold front will move southwards out of Canada on Saturday and Sunday, putting an end to this phase of the great heat wave of 2012. By early next week, temperatures will be near average for most of the eastern 2/3 of the U.S.

Quiet in the Atlantic
There are no threat areas to discuss in the Atlantic, and none of the reliable computer models are developing a tropical cyclone over the next seven days.

Jeff Masters