September heat wave will continue into Wednesday

Wednesday's high is forecast to reach the middle 90s, but we can expect temperatures to start gradually cooling down after Thursday, according to a meteorologist with the National Weather Service.

Students arrive for the first day of classes at Bluford Elementary School. Today is the first day of school for Philadelphia public school students, but 74 Philadelphia School District schools will dismiss early today due to extreme heat.Read moreAlejandro A. Alvarez / Staff Photographer

by Beatrice Forman

Updated Sept. 5, 2023, 6:00 p.m. ET

Published Sept. 5, 2023, 9:34 a.m. ET

The early September heat wave is slated to continue into Wednesday, with the National Weather Service forecasting another day of temperatures in the mid 90s with high humidity, resulting in heat index values exceeding 100.

The high temperature for Philadelphia on Tuesday was 94, just one degree shy of the record set in 2018.

The temperature at the Atlantic City International Airport also reached 94, and that was a record, the National Weather Service in Mount Holly reported.

Record highs were tied on Tuesday in Reading and Mount Pocono, in Pennsylvania, and Georgetown in Delaware.

Heat waves — which are marked by three consecutive days of 90-plus temperatures — happen about every five years in September in Philadelphia, though this one is on track to fall just short of the city’s longest hot spell, which lasted for six days in 1931, according to an Inquirer analysis.

Matt Brudy, a meteorologist with the National Weather Service in Mount Holly, said Thursday should be the week’s last “dangerously hot day,” though temperatures will likely remain high on Friday before dipping into the 80s over the weekend.

The persistent heat, which kicked off Sunday with temperatures in the low 90s and a record-setting Labor Day high of 95 degrees, comes from a wave of high pressure that’s rolling in from the Southwest, generating dry winds and repelling rains that could cool things down.

In keeping with the heat advisory that runs until Wednesday night, 74 schools in the Philadelphia School District that lack adequate air-conditioning will dismiss two hours early again on Wednesday, shortening days on the first week back in school. Decisions on future heat-related dismissals will be announced by noon the day before.

Despite the persistent thunderstorms, days filled with a soft orange smog from Canadian wildfires, and a last-ditch heat wave, this year’s meteorological summer was actually considered pretty normal — at least temperature wise.

From June 1 to Aug. 31, the average temperature at Philadelphia International Airport was 75.9 degrees. That’s the coolest since 2014 and just a hair below the 30-year normal determined by weather agencies with guidance from the World Meteorological Organization.

It looks like normal can usher in a whole lot of unusual.