After four steamy days in which being outdoors was as pleasant as standing in front of a hot pizza oven, the region is about to enjoy a run of splendid June weather. But the price of that enjoyment was a terrific - and sometimes destructive - cold front that wreaked havoc as it passed through tonight.

Emergency dispatchers in Montgomery and Chester Counties reported a flood of calls as trees snapped and power lines failed with the storm's arrival. Officials in Philadelphia, Delaware and Bucks Counties were not as busy, but had problems of their own.

Around 8:30 p.m., a variety of problems forced SEPTA to suspend Regional Rail service heading north of Market East, and some trains already on the tracks were disabled. A number of power outages and downed trees, including one that fell on the tracks near the 500 block of East Upsal Street in East Mount Airy that knocked the R7 line out of commission, interrupted service on the R2, R5, R6 and R8 lines.

"Believe me, there are many trees down," Gary Fairfax, a SEPTA spokesman, said last night.

Fairfax said SEPTA sent buses out to fetch stranded passengers, but some riders reported being stranded for hours or being let out at stations that were not their own.

Peco Energy Co. reported 141,000 customers without power shortly before 10 p.m., 120,000 of them in Montgomery and Chester Counties.

Cameron Kline, a Peco spokesman, said the damage was widespread and severe, and warned people that it might be a while before downed power lines could be repaired.

"This will be a multiple-day event for our customers," he said. "Wind, lightning and tree damage is extensive on our system."

And at Philadelphia International Airport, about 50 incoming and outbound flights had been canceled by about 9 p.m., and more were likely.

But returning to tomorrow's weather:

While the rest of the week should still be warm - and meteorologists warn that more extreme heat is all but inevitable this summer - it should feel downright refreshing after a spell that was about as hot as it ever gets around here before the solstice.

At least two deaths in Philadelphia were blamed on the heat. Both victims were found inside homes that lacked air-conditioning.

The official high today in Philadelphia, 98, broke the old record of 97, set in 1964, and it was the fourth straight day that temperatures had rocketed deep into the 90s.

"We're not used to Junes like this," said Joceyln Sirichio, who works in the Conshohocken office of the family roofing business, Joseph Del Buono Inc., whose employees have close encounters with heat.

More than 50 schools in Southeastern Pennsylvania and South Jersey shut down early yesterday, depriving students of precious opportunities to spend time in their favorite classes before schools shut down for the summer. Few complaints from schoolchildren were reported, however.

Heat is at its most dangerous in urban areas, health experts advise, and both confirmed fatalities occurred in Philadelphia. The windows were closed in the home of one of the victims, identified as Deborah Wright Jean-Louis, 65, of Overbrook. She was pronounced dead just before 2 a.m. today.

The other victim was identified as Genvieve Chmielewski, 82, who was found Monday in her home in Kensington.

In Delaware County, Marple Township police said a 14-month-old boy was hospitalized after being left in a vehicle for several hours in the heat when a relative forgot he was in the car, the Associated Press reported. The child was transferred to Children's Hospital of Philadelphia. There was no immediate word on his condition.

Even supermarket refrigeration cases couldn't keep up with the heat. Workers at the Whole Foods store at 20th and Callowhill Streets had to transfer prepared foods from several refrigeration cases after thermometers showed temperatures above acceptable levels.

Joel Singer, the bakery manager who was in charge of the store last night, attributed the problem to "the excess heat outside. All of our compressors are outside," he said, pointing to the roof. He said some of the store's air-conditioning had been off the previous day for servicing, which allowed the building to get warmer.

The "excessive heat" warnings have ended, but meteorologists are saying we would be well-advised to savor any respites the summer offers. Fresh rounds of oppressive heat - and hefty electric bills - during the next three months are all but inevitable, according to both government and commercial forecast services.

"If you start early, it's not a good sign," said Tony Gigi, a meteorologist in the National Weather Service's Mount Holly office.

June heat warms up the ocean, lessening the effect of cooling sea breezes, he said. It also dries out the soil. When the foliage is moist and lush, as it was at the start of the heat wave, it hampers the sun's ability to heat the ground. If the ground is dry in the next go-round, the sun won't have to use energy to evaporate moisture. Using a statistical analysis, the office is calling for summer temperatures to average 1.5 degrees above normal.

Accu-Weather, the commercial service in State College, Pa., also is calling for the summer to average 1.5 degrees above normal in Philadelphia.

And the government's Climate Prediction Center, citing recent trends of hot summers, sees a high likelihood of a hot summer here, said forecaster Mike Halpert.

"August and September will be remembered for being warm and steamy in Philadelphia," predicted Joe Bastardi, the long-range forecaster for Accu-Weather Inc.