Philly is under an ‘extreme heat’ warning as temperatures could hit 100 on three consecutive days
Philadelphia hasn't had three straight 100-degree days in 33 years.
The National Weather Service on Tuesday issued an “extreme heat” warning for the entire region through July Fourth, with a record-tying three consecutive days of 100-degree temperatures possible in Philadelphia.
While heat warnings may lack the sizzle of warnings for blizzards or hurricanes, health officials advise they can be more dangerous — slow-motion disasters that target the most-vulnerable populations. Plus, the timing of this one couldn’t be much worse.
Along with the daytime heat indexes approaching 110, the nights aren’t going to be much cooler. Temperatures Friday morning may not get below 80 degrees in the city, said Sarah Johnson, the warning coordination meteorologist with the National Weather Service in Mount Holly, which has been briefing emergency managers since late last week.
“It’s very concerning,” she said.
The city was expected to declare an emergency and activate its pioneering heat-response system.
The PJM Interconnection, region’s electric grid operator and one of the nation’s largest, already has sounded the alarm bells regarding power demands. Peco advised it has contingency plan in place in case workers go on strike Saturday, as they have threatened.
SEPTA is making preparations for what would have been a challenging week even if the weather was cool (as it was in 1776, by the way). At Philadelphia International Airport, a bigger concern would be pop-up thunderstorms that also could disrupt the weekend celebrations that have been 250 years in the making.
The heat wave is going to have some staying power in Philly
Only twice has Philly had three consecutive days of triple-digit temperatures — in 1993, and on July 2, 3, and 4 of 1966. That could happen again on July 2, 3, and 4 of 2026, the weather service says.
Tuesday’s forecast high in the low 90s would mark the second day this week and 16th day of the year that Philly officially hit 90 degrees. Wednesday’s forecast high, in the mid to upper 90s, would be the prelude to the holiday heat festival.
Along with the heat, of concern for event planners is the potential for strong thunderstorms on Saturday afternoon and evening during the climax of the semiquincentennial events.
Preparing for the heat and storm threats in the Philly region
At Philadelphia International Airport, it’s not the heat so much as the attendant storm threat that is the major concern, said spokesperson Heather Redfern.
The national extent of the extreme heat— the result of a so-called heat dome of high pressure — and the pop-up storm threat could “impact flights with delays, diversions to other airports and cancellations,” she said.
The airport was expecting more than 680,000 departing and arriving passengers from Wednesday through next Tuesday. Redfern advised travelers to sign up for airline flight alerts.
SEPTA would be reducing speeds on all rail lines, said agency spokesperson Andrew Busch, as extreme heat can cause overhead lines to sag and tracks to buckle.
The agency also expected a crush of passengers, especially Saturday when in addition to the 250th bash, a World Cup soccer game will be played in South Philly. He said SEPTA may set up misters outside stations where long lines may develop. The agency would try to make some cooling buses available if the city requests, he said.
A Saturday complication for Peco is a threatened strike by 1,500 union members. The company said it has a “contingency plan” in place to keep customers’ air-conditioning systems operating, and would be able to respond to any severe storm issues.
Heat-wave response is a Philly thing
It’s not in a league with the Rocky statue or cheesesteaks, but heat response is a very Philly thing that got its start in the 1990s when the city won high praise from the Centers for Disease Control and the National Oceanic and Atmospheric Administration.
The impetus was the summer of 1993 when Philadelphia recorded 118 heat-related deaths — about triple the the combined total of 2016-2015. That summer was also the last time the city had three consecutive days of 100-plus degree temperatures.
The relatively inexpensive program included setting up cooling centers; health officials hold that even a short break from extreme heat can save lives. Residents were urged to to check on elderly neighbors, and the Philadelphia Corporation for Aging set up a heat hotline.
Variants of Philly’s response system have spread to other cities around the country.
In Philadelphia, even though summer temperatures have been rising, heat-related deaths have declined dramatically.
May that trend continue.
Staff writer Ariana Perez-Castells contributed to this article.
