PHILADELPHIA - Summer is coming in like a fire-breathing dragon to the northeastern U.S.
The National Weather Service forecast potentially record-breaking hot temperatures just as the season officially starts Wednesday, the summer solstice and longest day of the year.
Readings are expected to approach or top 100 degrees Wednesday and Thursday in cities including Philadelphia, New York and Boston. Health officials warned residents to drink water, stay out of the sun and in air conditioning, and check on their elderly neighbors and on their pets.
After weeks of relatively mild June temperatures, Philadelphia may see the mercury soar to 97 and 99 degrees mid-week.
"We're very lucky that the pools opened yesterday," James Garrow, a spokesman for the Philadelphia health department, said Tuesday.
An area of high pressure off the East Coast, combined with a flow of warm, humid air coming from the South will heat things up, said Kristin Kline, a weather service meteorologist in Mount Holly, N.J.
Normally, the high for Philadelphia for the official start of summer is about 84 degrees, closer to Wednesday's predicted low of 80 degrees. The city's highs in the next couple of days could break decades-old records of 98 degrees, set in 1931, and 99, set in 1923.
"You're talking about almost 15 degrees above normal," Kline said.
The heat also will hit Boston-area residents hard. Triple digits are forecast in Boston - 101 degrees on Wednesday - followed by 99 on Thursday, the weather service said. Current record highs for these dates are 98 and 95 degrees, respectively.
New York City's 1.1 million public school students are still in session - until June 27 - and just 64 percent of the classrooms are air-conditioned. Temperatures are expected to hit 97 in the city both days.
Students were being advised to wear light clothing and drink plenty of water, and schools have been told to limit outdoor playtime, city Education Department spokeswoman Marge Feinberg said.
Forecasts for upstate New York on Wednesday and Thursday called for temperatures to break 90 from Buffalo to the Vermont border, with highs topping out in the mid-90s in some places.
The cities of Buffalo and Rochester, N.Y., opened several spray parks on Tuesday to help residents cool off as hot, muggy weather settled in. Buffalo doesn't normally open its 11 splash pads until July 1.
Philadelphia began a staggered schedule of opening its swimming pools, a couple of days after schools let out for the year. Nearly two dozen of the city's 70 pools will be open by Wednesday, with another seven opening Thursday.
Garrow said Philadelphia will activate its heat hotline at noon Wednesday and will work with personal care homes, senior centers, libraries and recreation centers to make sure air conditioners are running.
Officials will be setting up 114 "cooling centers" at facilities across the city, he said.
The Southeastern Pennsylvania Transportation Authority, the state's largest transit agency, is keeping a close eye on the heat as well, spokeswoman Jerri Williams said.
SEPTA, which operates trains, trolleys and buses in Philadelphia and its suburbs, planned to have extra maintenance workers to help deal with heat-related switch failures, problems with track expansion and any overhead wire issues on suburban train lines.
Moderate relief from the high mercury should come this weekend.