Author: Anthony R. Wood

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.

Though heat warnings may lack the sizzle of warnings for blizzards or hurricanes, health officials advise that 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 on Tuesday declared a “heat health emergency” in effect from 1 p.m. Wednesday through 8 p.m. Saturday, activating its pioneering heat-response system.

In deference to the heat, Wawa Welcome America announced several schedule changes, including canceling Thursday’s All-American Block Party, and moving back start times for concerts Thursday and Friday.

It also said the Liberty Medal ceremony on Friday honoring Pope Leo XIV would be moved to inside the Constitution Center and the route of the Semiquincentennial Parade, which begins at Fifth and Chestnut Streets, would end at Broad and Chestnut, rather than proceeding to Logan Circle as originally planned.

PJM Interconnection, the region’s electric grid operator and one of the nation’s largest, already has sounded alarm bells regarding power demands. Peco advised that it has a contingency plan 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 could disrupt the weekend celebrations that have been 250 years in the making.

The heat wave will have 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.

Officially it reached 90 degrees Tuesday at the airport, the 16th time this year that the high reached at least 90 degrees, the second-most number of days before Jul 1 in records dating to 1874. 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 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.

In its forecast discussion Tuesday, the weather service cautioned “that any holiday weekend festivities could be impacted by thunderstorms,” adding that “the environmental setup would be favorable for strong to severe” storms.

SEPTA was expecting a crush of passengers, especially Saturday when in addition to the 250th bash, a World Cup soccer match will be played in South Philly. The agency may set up misters outside stations where long lines may develop, spokesperson Andrew Busch said. 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.

With or without storms, in deference to the heat SEPTA will be reducing speeds on all rail lines, said Busch, as extreme heat can cause overhead lines to sag and tracks to buckle.

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 combined total of 2015-16. That summer was also the last time the city had three consecutive days of 100-plus degree temperatures.

The relatively inexpensive program includes setting up more than 50 cooling centers; health officials hold that even a short break from extreme heat can save lives. Residents are encouraged to look in on elderly neighbors, and the Philadelphia Corporation for Aging will be operating a heat hotline, 215-765-9040.

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.

The storms took down trees and wires, flooded roads, spoiled a World Cup party, and set off a deluge of smartphone panic alerts. But they evidently didn’t come close to erasing the rain deficits throughout the Philly region.

Even with the additional light rains on Tuesday, bringing the two-day total to about 1.45 inches, officially Philadelphia’s rainfall for June still is slightly below normal, and this is after an extraordinary streak of 10 consecutive months of below-normal precipitation.

And Monday’s storms exhibited a classic summer caprice. Areas of New Jersey and Chester County, both under state-declared drought emergencies, were all but stiffed, according to an analysis by the National Weather Service’s Middle Atlantic River Forecast Center. Northwestern Philadelphia and southeastern Montgomery County got as much as 2 inches.

The weather service’s Mount Holly office reported that totals within counties varied radically. In Bucks County, for example, 1.8 inches was measured in Bristol and just over a half inch in Doylestown. Across the river, 2.4 inches fell upon Sewell, and about 0.75 in Monroe Township.

“Some areas got it, some didn’t,” said Ben Casella, executive director of the New Jersey Farm Bureau. It can “rain here, but it may not rain on the other side of town,” he said.

Not all of that Monday rain was beneficial, said Andrew Frankenfield, educator with the Penn State Agriculture extension in Montgomery County. Some of the water in those downpours on Monday rushed to the gutters and didn’t stop to soak into the soil.

And those cloudbursts certainly weren’t beneficial to people routed from the World Cup fan fest in Fairmount Park, or to some motorists. Numerous water rescues were reported in the Wyncote section of Cheltenham Township, Montgomery County, And the weather service noted several reports of flooded streets and rushing water up to a foot deep floating cars in Germantown.

Tuesday’s gentle rains, Frankenfield said, were more beneficial to the plant life, which is only going to get thirstier as the summer progresses.

Is more rain coming to the Philly region?

Showers are possible Thursday, said Alex Staarmann, meteorologist with the National Weather Service in Mount Holly, with a better shot Friday night and Saturday.

However, these may again be lottery-ball situations, something with which farmers are well acquainted.

Generally throughout the region through Monday, precipitation was running about 75% of normal, on average about 5 inches below normal, according to the river center, which bases its surveys on several measuring stations in each county.

The latest interagency U.S. Drought Monitor map had most of the region in “moderate drought,” but Cape May County and areas of New Jersey near Delaware Bay are in “extreme drought.” Those regions were all but shut out from the Monday downpours.

They evidently fared a bit better on Tuesday, with the Millville airport reporting about a third of an inch, and a half inch measured in Sea Isle City.

While the rains were welcome, the drought anxieties persist, Casella said.

“As we turn the calendar into July, the crops are going to need more moisture,” Frankenfield said.

“We certainly need more” rain, he said. “We can’t make it up in a week, we can’t make it up in a month. We’re concerned, but not alarmed.”

It would have nothing to do with Arthur, which on Wednesday became the first named storm of the Atlantic hurricane season, but the Philly region may be in for tropical-storm force gusts and strong thunderstorms Thursday.

Even if the rains don’t come — and on Wednesday, the storm odds were close to 50-50 — wind gusts to 45 mph are possible during the afternoon, said Alex Staarmann, meteorologist at the National Weather Service in Mount Holly, “quite unusual for June.”

Not so unusual these days would be the forecast high, which would mark the 14th time this year that official readings in Philly had reached 90 degrees or higher. That is about half the average total for an entire year.

But this heat will be more of a ripple than a wave, and the outlook for the holiday weekend is looking spectacular.

When the winds and storms may arrive in Philly on Thursday

As a front approaches, winds from the southwest are expected to gust to 20 mph during the morning and 30 to 40 mph in the afternoon.

While the winds are all but a certainty, it was unclear if any strong storms would pop Thursday. If they did, the best estimate would be between 1 an 8 p.m., the weather service said.

“The environment is favorable for damaging winds if anything does develop,” Staarmann said.

“The biggest question is how widespread the storms are going to be,” he said.

Uncertainty is a near 100% certainty with June storms

Such uncertainty is standard fare with thunderstorm threats this time of year, said Rich Thompson, forecast operations branch chief at the government’s Storm Prediction Center, which would have to make a call on posting severe storm watches.

With so many moving parts and micro-features such as terrain involved, predicting the behavior of small-scale storms is “incredibly complicated,” he said, and on some days clues are frighteningly lacking.

And while observations have improved immeasurably in recent decades, “we still aren’t observing most of what’s there,” he said. Land-based surface observations are far more plentiful than those over the oceans, which cover 70% of the atmosphere, and in the upper atmosphere, where the weather is manufactured.

Even if the atmosphere were perfectly measured, he added, meteorologists would still have to contend with the fact that the physics involved in forecasting are not completely understood.

Arthur and the weekend outlook for Philly

As for Arthur, knighted with a name by the National Hurricane Center at 11 a.m. Philadelphia time Wednesday as it matured off the southeast Texas coast, it is forecast to deluge portions of the Gulf states.

Then it is due to head out to sea before it could have anything to do with Philadelphia or the Jersey Shore, which is likely to be a popular destination this weekend.

For Friday, Juneteenth; Saturday; and Sunday, the beginning of the astronomical summer, highs are expected in the mid-80s with sunny days and no threat of showers until early Monday.