Heat indexes at the Jersey Shore hit 105 Tuesday, according to the National Weather Service, and crested past triple-digit on the mainland.
For those who sought refuge in the Atlantic Ocean, surf temperatures were near 80 Tuesday afternoon, what weather service meteorologist Dean Iovino called "bath water."
The Philadelphia School District already had made the preemptive announcement would close at 1 p.m. Tuesday and Wednesday, when temperatures were forecast again to reach the mid-90s with heat indexes over 100.
The official high at Philadelphia International Airport on Tuesday, 94, was the highest reading since July 16, but well short of the record, 99, set in 1973.
At least one school district, Tredyffrin/Easttown in Chester County, unexpectedly announced it was closing its elementary schools early because of the heat after students had started classes Tuesday morning.
The weather service warned that in the urban corridors temperatures might not get below 80 Wednesday morning, and it's possible that a record will be set overnight for the highest minimum temperature for an Aug. 29 in the city. National Weather Service has issued a heat advisory that remains in effect through 8 p.m. Wednesday and extended it Tuesday to cover a wider area.
Heat advisories were in effect throughout parts of the Northeast, all the way to the Canadian border. An "excessive heat warning" was up for eastern Massachusetts, including the Boston area.
But around here in what would mark a dramatic departure from the relentless sogginess of recent weeks, which has been an absolute dream for the region's foliage and fungal life, not a drop of rain is in the forecast until at least Thursday. That would mark the first seven-day period without at least a trace of rain officially in Philadelphia since Thanksgiving week.
Since July 1, the National Weather Service office in Mount Holly has issued flash flood watches in its coverage area on no fewer than 15 days. Rainfall has been substantially above normal in the city in the last 60 days, according to the Middle Atlantic River Forecast Center — and around double normal in Chester and Montgomery Counties, 17 inches and 16.1, respectively.
In addition to taxing people in charge of mowing lawns, the rains have wrought a "pretty spectacular" harvest of mushrooms and assorted fungal plants, said Pennsylvania State University's David Geiser, who is a mycologist, or mushroom expert.
"The diversity is great," he said. "For mycologists, it's exciting."
But if you encounter mushrooms in the wild, cautions Geiser, watch what you eat. In North Jersey, an area also hammered by downpours, an outbreak of mushroom-related illnesses has been reported.
"I would not collect wild mushrooms unless I knew what I was doing," said Geiser. He recommends consulting an Audubon guide or mushroomexpert.com.
Geiser said he knew of no similar mushroom-illness outbreaks in Pennsylvania, but "there's lots of poison mushrooms all over the state."
Children's Hospital of Philadelphia hasn't seen an uptick in poisoning incidents, said Jeanette Trella, CHOP's managing director of the Poison Control Center.
"We have, however, seen a noticeable spike in traffic to our mushroom web page this summer," she said.
But this will not be a particularly rewarding week for thirsty fungi. Even the forecast for Thursday only mentions a prosaic "chance of showers."
Right now, the region's atmosphere is under the influence of a classic Bermuda high pressure system that is transporting warm, humid air northward, said Lee Robertson, a weather service meteorologist in Mount Holly.
Still, overall this has been a benign summer in Philadelphia, with only one prolonged heat wave, from June 29 through July 5, and a milder one from Aug. 5 through 8.
And so far, the city has reported only one heat-related death.