As scorching temperatures expand across the U.S., will the Lehigh Valley see a heat wave next week?

BETHLEHEM, Pa. — Hot summertime conditions will expand across the United States in the middle of next week, bringing the Lehigh Valley its hottest temperatures of the year thus far.

That’s the update from the government’s Climate Prediction Center, which puts the region at a 60-70% chance of above-average temperatures from July 26-30.

• The Lehigh Valley could see its first official heat wave of the year next week
• It comes as forecasters expect hot, summertime conditions to expand across the United States
• The entire planet has surged to record heat both in June and July

It could bring the Lehigh Valley’s first official heat wave of the year, pushing temperatures into the 90s.

What is a heat wave?

Meteorologists apply the label “heat wave” to areas where temperatures are above the historical average for two or more days.

But the definition can vary by region; in the Mid-Atlantic and Northeast, a heat wave is defined as three straight days of temperatures at or above 90 degrees.

According to the National Weather Service, temperatures will top off in the mid- to upper 80s on Monday and Tuesday, then gradually warm through next week.

Temperatures in the area should be in the upper 80s to around 90 on Wednesday, then in the low 90s through the rest of the week.

The heat index — an estimate of how hot it feels when air temperature and humidity are combined — also will be on the rise as dew points eventually creep back up into the upper 60s and low 70s.

Heat advisories are generally issued when the heat index is forecast to reach 95 to 99 degrees for at least two consecutive days, or 100 to 104 degrees for any length of time.

Will the heat last?

The entire planet has surged to record heat both in June and July, but the Lehigh Valley and the rest of the Mid-Atlantic and Northeast have largely been spared.

A lot of that has to do with El Niño and the orientation of the jet stream, EPAWA meteorologist Bobby Martrich said last week.

El Niño brings warm water to the equatorial Pacific Ocean and also leads to higher global average temperatures.

The Earth just had its hottest June on record, and nearly every day of July, the global average temperature has been warmer than the unofficial hottest day recorded before 2023, according to the Associated Press, citing the University of Maine’s Climate Reanalyzer.

Scientists say climate change and El Niño have been the major drivers of the extreme heat.

“We do expect the El Niño to at least continue through the northern hemisphere winter. There’s a 90% chance or greater of that,” NOAA meteorologist Matt Rosencrans said in a teleconference Thursday.

For the Lehigh Valley, Martrich said he expects warmer-than-average temperatures “in short spurts here and there, but nothing extreme" right now.