At the Washington, D.C., Fourth of July celebrations Saturday, large water cannons sprayed attendees struggling with extreme heat. Emergency workers were deployed to assist people with heat-related conditions, with some attendees being evacuated on stretchers to receive medical aid. Cases of water bottles were stationed throughout the outdoor venue, and the temperature of the outdoor chairs reached 160 degrees.

Thunderstorms caused by the clash of warm and cool air impeded the festivities, with attendees seeking shelter in makeshift tents. Severe thunderstorm weather with winds gusting to 65 mph stretched from Missouri to Pennsylvania.

A heat dome blanketing large swaths of the United States and pushing air downward, causing temperatures to rise above 100 degrees in some places, such as Philadelphia, Pa., and Washington, D.C., may have resulted in as many as 25 deaths. In New Jersey alone, 22 heat-related deaths were reported, mostly people in their 30s to 80s and mostly in homes that lacked air conditioning.

The National Weather Service predicted that cooler air will push the heat dome south and west, providing relief to the Northeast.