The current map of weather watches and warnings from the National Weather Service prominently shows vast areas of the northwest, East Coast, and heartland with a high heat index over the next few days.

The magenta color in the northwestern US and around New York and Boston indicates areas now under an “excessive heat warning.” More than 56 million people live in these areas. The orange color in the heartland and along the East Coast from Maine to North Carolina represents about 62 million people under a heat advisory.
As of this afternoon, the Washington Post reported that at least 175 million Americans were under excessive heat warnings or heat advisories.
And this heat wave isn’t just happening around Washington or Washington State.
Hey it's National S'more Day! All you need to do is walk outside with your graham crackers, chocolate, and marshmallow and everything should start melting. If your marshmallow catches on fire we suggest going back inside. 🍫🔥🥵 pic.twitter.com/SMhB4pS6JZ
— NWS Kansas City (@NWSKansasCity) August 10, 2021
“A heat warning means that some people can be seriously affected by heat if precautions are not taken,” the National Weather Service warns. “Studies in Canada, Europe, and the US have indicated that mortality begins to increase exponentially as the heat increases or stays above a heat index of 104°F.
“In addition to raising public awareness, the issuance of a heat warning will alert hospitals and officials to take certain actions to prepare and respond to an increase in emergency calls, and activate programs to check on elderly and the home-bound. In some cases cooling centers can be open or designated and donation programs activated for fans and air conditioners. As in the case of an advisory, certain regulations may change such as turning off people’s electricity, evictions, and outside work requirements.”