2001 eastern North America heat wave

A rather cool and uneventful summer along the East Coast of the United States (with a more average heat pattern occurring in the Midwest/Great Lakes regions) changed abruptly when a ridge of high pressure centered off the coast of South Carolina strengthened in late July. It began in early August for areas of the Midwest and western Great Lakes before spreading eastward and intensifying.

Source: Wikipedia — 2001 eastern North America heat wave (CC BY-SA 4.0)