The National Weather Service forecast potentially record-breaking hot weather just as the summer officially starts.
Temperatures are expected to approach or top 100 degrees Wednesday and Thursday in cities including Philadelphia, New York and Boston.
Officials advise residents to drink water and stay out of the sun and in the air-conditioning.
In western New York, the city of Buffalo opened several spray parks about 10 days early to help residents cool off as hot, muggy weather settled in on Tuesday.
Relief from the high mercury should come this weekend.
