A prolonged and dangerous heat wave will dominate the weather story this week as much of the central and eastern United States experiences some of the hottest weather of the year. Heat index values above 100 degrees will become widespread, with some communities seeing readings between 105 and 115 degrees and little relief at night. At the same time, several rounds of severe thunderstorms are expected from the High Plains through the Upper Midwest and Northeast, bringing the threat of damaging winds, large hail, and localized flash flooding. Out West, cooler-than-normal temperatures will continue while dry conditions keep wildfire concerns elevated across parts of the Four Corners and Great Basin. Air quality is an issue across Alberta to Quebec due to wildfire smoke. Heavy precipitation is possible from far eastern Saskatchewan to far western Manitoba.