NEW YORK — The high temperatures that made life hot and miserable throughout the Northeast are expected to return, with readings in the mid- to high-90s.

Water-guzzling residents who stayed close to their air conditioners will have to get through today before temperatures are expected to start cooling down.

Wednesday, the first official day of summer, saw recordsetting temperatures from New York City to Burlington, Vt.

Several relatives of high school graduates were treated for heat exhaustion at an outdoor 

ceremony in North Bergen, N.J., and taken to a hospital. Ambulances were on standby at the event, which was held outside to accommodate about 5,000 people, said Capt. Gerald Sanzari of the North Bergen Police Department.

A similar scene took place in New Britain, Conn., where several people were taken to a hospital after suffering heatrelated symptoms while attending the New Britain High School graduation. Capt. David Koscuk of the New Britain EMS told the New Britain Herald that 24 people suffered from heat exhaustion or fainting and half of them were taken to area hospitals.

According to the National Weather Service, it hit 94 degrees at New York’s John F. Kennedy International Airport, passing the 93-degree mark set in 1995. The 98- degree temperatures at LaGuardia Airport and Newark Liberty International Airport passed records set in 1953, when highs reached 96 at LaGuardia and 97 at Newark.

In New England, the mercury hit 97 degrees at Bradley airport in Hartford, Conn., breaking the 1995 record of 96 degrees. Record temperatures were also seen in Burlington, Vt., and Houlton, Maine, which reached 95 degrees and 90 degrees, up from 94 and 89.

Residents of the Mid-coast region seemed to take the heat in stride. Other than a report of young people tossing water balloons at vehicles, Brunswick police said they did not handle any weather-related calls.

Popham Beach State Park in Popham quickly filled with people seeking relief from the heat at the seashore.

Even places that didn’t break records were extremely hot. In Washington, the airports topped out at 98, just shy of setting new heat marks. The mercury in Philadelphia rose to 97 degrees, one degree short of the record of 98 set in 1931.

Every state in the Lower 48 except for North Dakota was forecast to have 90-degree weather until Saturday, according to a model by the National Oceanic and Atmospheric Administration, the agency in charge of weather, climate and oceans.

Deborah Otchere, 59, mapped out a tree-lined route to work and brought a change of clothes to her job as a secretary in a Washington law firm. Among her traveling supplies was a partially frozen bottle of water.

More than 450 cooling centers were being opened around New York City, which is under a hot weather advisory. Mayor Michael Bloomberg encouraged people without air conditioning to seek out the cooler spaces or visit the city’s beaches.

On New York’s Long Island, Roy Gross, chief of the Suffolk County SPCA, cautioned against keeping pets in vehicles, noting temperatures can reach 120 degrees within minutes.

“Your pet can quickly suffer brain damage or die from heatstroke when trapped in these high temperatures,” Gross said.