The National Weather Service has upgraded the previous Extreme Heat Watch to an Extreme Heat Warning for parts of Pennsylvania and New Jersey as a dangerous stretch of heat and humidity moves into the region.
The warning will be in effect from noon Wednesday through 8 p.m. Saturday.
The warning includes Berks, Lehigh, Northampton, Upper Bucks, Western Chester, and Western Montgomery counties in Pennsylvania. In New Jersey, it includes Morris, Sussex, Warren, and Hunterdon counties.
Forecasters say heat index values are expected to reach 100 to 110 degrees each day, with the hottest conditions expected Thursday and Friday.
Very warm overnight lows in the low to mid-70s will offer little relief from the heat. The National Weather Service says the combination of extreme daytime heat, humidity, and warm nights will increase the risk of heat-related illness.
An Air Quality Alert is also in effect Tuesday for the Philadelphia metro area, including Upper Bucks, Lower Bucks, Montgomery, Chester, Delaware, and Philadelphia counties. A Code Orange alert means air pollution may become unhealthy for sensitive groups, including children, older adults, and people with asthma, heart disease, or other lung conditions.
Residents are urged to drink plenty of fluids, stay in air-conditioned spaces, avoid the sun when possible, and check on relatives and neighbors.
Officials also remind the public to never leave children or pets inside unattended vehicles. Interior temperatures can become deadly within minutes.
Anyone working or spending time outside should wear lightweight clothing, take frequent breaks in shaded or air-conditioned areas, and limit strenuous activity to the early morning or evening.
Heat stroke is an emergency. Anyone overcome by heat should be moved to a cooler location immediately, and 911 should be called.
