Key Facts

• The heat dome covers much of the central and eastern U.S., causing "major-to-extreme" heat risk according to the National Oceanic and Atmospheric Administration (NOAA).
• The heat index, which factors in humidity to show how hot it feels, is expected to reach 113-115 degrees in several eastern cities, higher than Death Valley's 102-degree heat index forecast.
• Cities like Washington, D.C., New York, Philadelphia, and multiple Virginia and Maryland locations will experience peak heat indices over 110 degrees.
• At least 28 states across the Midwest, Great Lakes, Mid-Atlantic, Northeast, and Southeast have heat warnings or advisories as of Friday morning.
• Forecasters predict storms and wildfire smoke in some areas, with a chance of tropical development near the southern Atlantic or Gulf coasts over the holiday.
• The heat will coincide with World Cup soccer knockout games in Philadelphia and New Jersey, where temperatures are forecast to be near 101 and 89 degrees, respectively.
• Tips to stay cool during the heatwave include using cool, damp cloths on pulse points, freezing damp towels for relief, chilling pillowcases before sleep, soaking feet in cool water, and eating water-rich frozen snacks.