NEW YORK (AP) - Temperatures climbed toward the high 90s along the Eastern Seaboard on Wednesday as an unusually early hot spell heralded the official start of summer, with people wilting at graduation ceremonies, students trying to learn in suffocating classrooms and authorities warning folks to check on elderly neighbors.

The National Weather Service has forecast heat in the mid- to high 90s in cities including Boston, New York, Philadelphia and Washington. Health officials warned residents to drink water, stay out of the sun and in air conditioning, and to check on elderly neighbors and pets. Public cooling centers have been set up in dozens of cities for those without air conditioning.

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, police told The Record of Bergen County. 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.

In Howell, N.J., school officials made Wednesday the last day of the school year instead of today, citing the heat. And at nearby Wall High School, people attending the graduation ceremony will be able to watch a remote broadcast inside the air-conditioned building.

Connie Vincent, a mail carrier, was already sweating as she began her rounds in a residential neighborhood in Manchester, Conn., Wednesday morning.

"There's nothing you can do," she said as she dabbed her face with wet washcloths. "Tomorrow's my day off, thank God. I've just got to make it through today."

In a rare bending of the rules, the Metro in Washington, D.C., said passengers on Wednesday and today would be allowed to drink water, an exception to their no-drinks policy. The National Weather Service said the temperature at Washington National Airport was 95 degrees just before 2 p.m.