Temperatures could feel close to 100 over the next few days in the Lehigh Valley.

Lehigh and Northampton counties, along with nearby Berks, Bucks, Carbon and Monroe, are under a heat advisory starting 10 a.m. Thursday, according to the National Weather Service in Mount Holly, New Jersey.

The Lehigh Valley, Berks and upper Bucks counties are under the advisory until 8 p.m. Friday. The advisory lifts at 8 p.m. Thursday for the northern part of the advisory, in Carbon and Monroe counties, and 8 p.m. Saturday for the southern parts, in Lower Bucks and Philadelphia.

Forecasters said Thursday will kick off a stretch of prolonged period of heat for the area. Very humid conditions are expected over the next several days.

“We look to have a weak cold frontal passage early Sunday, ushering in slightly drier air,” meteorologists wrote Thursday in their daily forecast discussion. |This will give some slight reprieve from the excessive humidity, though highs will still be in the upper 80s to low 90s.”

🥵⛈️ An extended period of hot and very humid conditions begins today. Highs in the upper 80s to low 90s, but very high humidity will cause heat indices in the upper 90s to low 100s. Similar conditions expected each day through early next week. (1/2) #PAwx #NJwx #DEwx #MDwx pic.twitter.com/retxJzOSeF

— NWS Mount Holly (@NWS_MountHolly) August 6, 2026

Forecasters said people should stay hydrated and take precautions when they go outside. Strenuous outdoor activities should be limited to the evening or morning, the weather service said.

There is a possibility of scattered showers or thunderstorms through Saturday and much of next week.

Here is the extended forecast from the National Weather Service:

Friday: A chance of showers and thunderstorms after 2 p.m. Patchy fog before 9 a.m. Otherwise, mostly sunny, with a high near 89. Calm wind becoming southwest around 5 mph in the afternoon. Chance of precipitation is 30%. New rainfall amounts of less than a 10th of an inch, except higher amounts possible in thunderstorms.

Saturday: A chance of showers and thunderstorms after 2 p.m. Mostly sunny, with a high near 89. Light southwest wind increasing to 5 to 10 mph in the afternoon. Chance of precipitation is 30%. New rainfall amounts of less than a 10th of an inch, except higher amounts possible in thunderstorms.

Sunday: Sunny, with a high near 89.

Monday: Mostly sunny, with a high near 90.

Tuesday: A chance of showers. Mostly sunny, with a high near 91. Chance of precipitation is 40%.

Wednesday: Mostly sunny, with a high near 85.