Temperatures on the rise, with near-record heat expected Wednesday

BETHLEHEM, Pa. — Don’t close your swimming pool just yet.

After temperatures that felt more like October than August last week, forecasters say the Lehigh Valley will return to summer in a big way this week.

Heat and humidity will build day-to-day, culminating with record-challenging temperatures Wednesday, according to the National Weather Service.

Monday afternoon, the weather service updated its forecast, calling for an excessive heat watch from Wednesday afternoon into the evening.

The record high for Aug. 28 in the Allentown area is 97 degrees, with the forecast currently calling for a high of 95. With an excessive heat watch, heat indexes could reach upwards of 105 degrees.

'Very warm through midweek'

“It’s going to be very warm through midweek,” EPAWA meteorologist Bobby Martrich said in his latest video update.

“We have some ridging moving into the region that started building a little bit over the weekend, and it’s going to be getting progressively warmer every day,” Martrich said.

That will put temperatures Monday “a degree or two higher than Sunday” and Tuesday’s temperatures “another degree or two higher than Monday.”

But the peak heating day is going to be Wednesday, Martrich said.

“That’s going to be the day it’s going to be very, very summer-like with some oppressive heat and humidity,” he said.

Wednesday kicks off the first night of the Allentown Fair, which opens its 172nd run with Cheap Trick headlining.

The fair continues through Labor Day, Monday, Sept. 2. Hours are 4-10 p.m. Wednesday, noon to 10 p.m. Thursday through Sunday and noon to 9 p.m. Monday.

Heat to be cut down by storms?

“The good thing is, if you’re not a fan of [the heat], it’s only a day,” Martrich said.

Later Wednesday we’ll have a cold front approaching that will quickly scrub out the heat, with the possibility of late-day showers and thunderstorms.

The Storm Prediction Center has all of Pennsylvania at a slight risk (2 out of 5) of severe weather, though it said uncertainty remains with evolution, “as substantial model differences exist.”

Risk areas are “likely to require adjustment,” the SPC said in its Day 3 outlook, but said “current indications are that storms should re-intensify/develop during the afternoon.”

Damaging winds are likely to be the primary threat, with storms likely to continue well into the evening and possibly into the overnight hours, the SPC said.

But right now, Martrich said models show just an isolated chance for storms and things don’t look too impressive.

Behind the front, the long-term period looks to be increasingly unsettled as we head into Labor Day weekend, the weather service said, with “plenty of shower and storm potential around but with embedded dry periods as well.”