100-plus tomorrow almost a sure thing

Usually, a 20 m.p.h. breeze on a summer day would provide a degree of refreshment, but this afternoon it was about as refreshing as a blast from a hot hair dryer.

And tomorrow it gets only more unpleasant, with the temperature expected to make a run at the record and reach 100 for the 60th time since Philadelphia began keeping track back in 1874.

The heat index - what it "feels like" - could go as high as 110 to 112, the National Weather Service said. To put that in perspective, the heat index today peaked at 107 on a day when the high, 98, came up shy of the record, 103, set in 1930.

The weather service's excessive-heat warning remains in effect until 8 p.m. Saturday all the way from the Poconos to the New Jersey and Delaware beaches.

Nothing in weather is a sure thing, but for three days now, the computer models have been seeing 100-degree readings for tomorrow in Philadelphia, said Jim Hayes, a meteorologist with the weather service office in Mount Holly. The official forecast is calling for 103, and the July 22 record is 100, set in 1957, 1955, and 1926.

He added that the air is unusually moist for readings that high. Water vapor tends to inhibit heating because some of the sun's energy is diverted to evaporating the water.

"This is very atypical," said Hayes.

The breezes from the southwest probably are bringing some moisture off the Chesapeake Bay, said Alex Sosnowski, a meteorologist with Accu-Weather Inc.

It is possible that some dryer air will mix down from the mountains to the west and lower the discomfort levels this evening, he said. But it won't be much in the way of relief, and it's not going to last very long.

The weather service is warning of continued "dangerous" heat and sweltering nights in which temperatures will fight to get below 80.

During those unusually hot nights, the rowhouses inhabited by so many of the elderly and vulnerable don't get a chance to cool off, and they warm up quickly after the sun comes up. Thus, officials fear those conditions could lead to heat-related deaths. At least three have been reported in Philadelphia so far this year.

The ridge of high pressure that has the region in a pressure cooker isn't expected to start breaking down until late Saturday. After that the extreme heat backs off, but it stays quite warm, with daytime highs around 90 into next week.

"We're still anticipating a breakdown of this nasty heat," said Sosnowksi, "but it may be replaced by high humidity."

That would mean an enhanced chance of cooling thunderstorms, he noted, a time when the foliage could use it.

Said Sosnowski: "My grass looks like Shredded Wheat."

The Philadelphia Corporation for Aging in the meantime has activated its Heatline - 215-765-9040 - for anyone seeking information on coping with the heat. The information line will operate until midnight tonight, from 8:30 a.m. until midnight Friday, and 8:30 a.m. until 8 p.m. Saturday.