BETHLEHEM, Pa. — The National Weather Service has placed much of the state, including the Lehigh Valley, under an extreme heat watch for the front half of next week.
It’s the first issued since the NWS renamed its heat watch and warning products to improve messaging of hazards and provide better decision-making services.
Under the new system, an excessive heat watch and warning were renamed to extreme heat watch and warning.
The NWS said it acted upon data collected during public and partner engagements, surveys and social science research, leading to the renaming of the products.
The name change seeks to improve communication and messaging of hazardous heat and better convey that heat is dangerous.
It aligns with the extreme cold watch and warning products used in the winter, the agency said.
First 90-degree day, heat wave
The watch is in effect from Monday morning through Wednesday evening next week, with dangerously hot conditions expected.
Heat index values up to 107 are possible, the weather service said.
The Lehigh Valley fell one degree shy of 90 on Thursday, meaning the upcoming heat wave also will bring the first official 90-degree day of the year.
Historically, the Lehigh Valley usually sees its first 90-degree day by May 24.
With the arrival of the summer solstice late Friday night, the summer benchmark now will fall inside of astronomical summer.
Temperatures are expected to soar into the 90s over the weekend, with these high temperatures expected in the coming days:
Saturday: 87 degrees
Sunday: 92 degrees
Monday: 97 degrees
Tuesday: 96 degrees
Wednesday: 92 degrees
Low temperatures will hover near 80 degrees in urban areas during this stretch, and in the low to mid 70s in the Lehigh Valley.
“Heat will have a cumulative effect on the body as the week goes on as little relief will come overnight,” the watch states.
‘Widespread triple digit heat indices’
The weather service said the combination of air temperatures well into the 90s and dew points in the upper 60s to low 70s will result in widespread triple-digit heat indices.
“With high confidence in heat indices getting to/exceeding 105, went ahead with an extreme heat watch Monday through Wednesday,” the latest forecast discussion said.
The hottest temperatures of the season for the Central and Eastern U.S. are forecast to begin Friday and carry through the weekend as summer makes its presence known to a large portion of the nation. pic.twitter.com/zOhC5Yrw2O
— NWS Weather Prediction Center (@NWSWPC) June 16, 2025
“Other factors considered with the early watch for next week were the quick ramp up in temperatures (most of June has been below normal), the lack of relief at night, and the potential duration of this event.”
It said heat advisories may be needed as early as Sunday and continue potentially all the way to Thursday.
