BETHLEHEM, Pa. — A stretch of potentially record-breaking heat is set to grip the Lehigh Valley this week.
An expansive "heat dome" spreading across much of the United States will push temperatures far above normal for mid-April, according to the National Weather Service.
If the Allentown area reaches 90 degrees, it would mark the first 90-degree day of 2026 and the first since Aug. 17, 2025.National Weather Service
Weather service forecasters say highs in the region will surge into the low to mid-80s Tuesday, followed by upper 80s to near 90 degrees Wednesday and possibly Thursday.
That would be as much as 15 to 30 degrees above average for this time of year.
If the Allentown area reaches 90 degrees, it would mark the first 90-degree day of 2026 and the first since Aug. 17, 2025.
The unusual warmth is tied to a large, slow-moving area of high pressure — often referred to as a heat dome — that already has shattered temperature records across the western and central United States and now is heading east.
'The entire U.S. is going to be hot'
Meteorologists say the scope of the heat is what stands out most.
“Basically the entire U.S. is going to be hot,” National Weather Service meteorologist Gregg Gallina told the Associated Press.
“The area of record temperatures is extremely large. That’s the thing that’s really bizarre.”
The warmest low ever recorded in Allentown on April 14 is 61 degrees, with similar unusually mild nighttime records in the upper 50s to low 60s for the following days.National Weather Service
Climatologists say the event could rank among the most geographically expansive April heat waves on record, though not as intense as peak summer extremes.
In the Lehigh Valley, the focus turns to whether daily records — many of which have stood for decades — will fall.
At Lehigh Valley International Airport, the record high for April 14 is 88 degrees, set in 2023. The mark for April 15 is 86 degrees, set in 1941 and tied in 1994, while April 16’s record stands at 90 degrees, set in 2012.
Overnight temperatures also could challenge records.
The warmest low ever recorded in Allentown on April 14 is 61 degrees, with similar unusually mild nighttime records in the upper 50s to low 60s for the following days.
'This is not just a one-day spike'
Even if records aren’t broken, forecasters say the prolonged stretch of warmth is notable for its consistency and timing.
“This is not just a one-day spike,” the weather service said in its forecast discussion. “Very warm and above-normal temperatures will continue through the upcoming weekend.”
The bigger concern may be what’s missing: Rain.National Weather Service
Despite the heat, humidity levels are expected to remain relatively moderate compared with summer, which may limit how oppressive conditions feel. Winds also are expected to stay light.
The bigger concern may be what’s missing: Rain.
Little to no precipitation is expected through the week, which will worsen ongoing drought conditions across eastern Pennsylvania.
A weak front is expected to move through late Thursday into Friday, but it will do little to cool things down.
Temperatures are forecast to remain well above normal into the weekend, with highs generally in the low 80s.
For residents, the week ahead may feel more like mid-summer than mid-spring, with the potential for record books to reflect it.
