An excessive heat advisory is in effect from noon today until 9 p.m. across the Delaware Valley, according to the National Weather Service.
Affected counties include Philadelphia, Bucks, Montgomery, Delaware and Chester, in Pennsylvania.
In New Jersey, the affected counties are Gloucester, Camden, northwestern Burlington and Mercer.
Temperatures are expected to rise to the low to mid 90s today, which could be life threatening for those who without air conditioning or who work outside during the hottest time of the day, the weather service warns.
Tonight is expected to be mostly clear with lows in the mid 70s.
At the Jersey Shore, an air quality advisory and hazardous weather alert are in effect today, with a moderate rip currents and a heat index approaching 95 degrees this afternoon, the weather service said.
Tuesday is expected to have highs in the lower 90s. Rain is not expected again until Wednesday.