The air could be unhealthy for certain groups of people Monday in Berks as a heat wave brings near-record temperatures to the region.

The Pennsylvania Department of Environmental Protection has placed Berks, Chester, Delaware, Lehigh, Northampton and Philadelphia counties under a code orange air quality alert for ground level ozone. After starting out in a yellow air quality alert, it is expected to reach well into the orange zone by the afternoon.

People with lung disease, children and teens, older adults and people who are routinely outdoors for more than six hours should reduce their exposure by choosing less strenuous activities or shortening the amount of time outdoors, according to AirNow.gov.

Highs will peak in the lower and middle 90s, which will ramp up ozone production through the day, the website states.

🥵🌤️ The first of 3 hot days begins today, with temperatures reaching into the low to mid 90s in many areas this afternoon. Record highs will be challenged through Wednesday, and even some monthly records for May challenged on Tuesday. Stay cool out there! #PAwx #NJwx #DEwx #MDwx pic.twitter.com/HMMihKeqiD

— NWS Mount Holly (@NWS_MountHolly) May 18, 2026

Temperatures in the 90s are expected through Wednesday, and highs could set records each day, according to the weather service.

A cold front will drop highs back into the 60s and 70s starting Thursday.

Here is the extended forecast from the weather service:

Monday: Sunny, with a high near 94. Southwest wind 5 to 10 mph.

Monday Night: Mostly clear, with a low around 69. South wind around 5 mph.

Tuesday: Mostly sunny, with a high near 95. Light southwest wind increasing to 5 to 10 mph in the afternoon.

Tuesday Night: Partly cloudy, with a low around 72. Southwest wind around 5 mph.

Wednesday: Showers and possibly a thunderstorm after 2 p.m. High near 90. West wind 5 to 10 mph, with gusts as high as 20 mph. Chance of precipitation is 90%. New rainfall amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

Wednesday Night: Showers, mainly before 8 p.m. Low around 54. Chance of precipitation is 80%. New precipitation amounts of less than a tenth of an inch possible.

Thursday: Partly sunny, with a high near 70.

Thursday Night: Mostly cloudy, with a low around 50.