WASHINGTON (AP) - The mercury climbed into the 90s across half the country Wednesday in a record-breaking blast of August-like heat, forcing schools with no air conditioning to let kids go home early and cities to open cooling centers. And scientists say we had better get used to it.

A new study from Stanford University predicts that global climate change will lead permanently to unusually hot summers by the middle of the century.

Temperatures in the 90s were recorded across much of the South, the East and the Midwest. Baltimore and Washington hit 99 degrees, breaking high-temperature records for the date that were set in 1999, according to the National Weather Service. The normal high for the date is about 82.

Philadelphia hit 97 degrees, breaking a 2008 record of 95, and Atlantic City, N.J., tied a record of 98 set in 1999. Chicago reached 94 by midafternoon. The temperature hit 97 in LaGuardia, N.Y., breaking the old record of 96 set in 2008. Newark, N.J., reached 99 degrees, breaking a record of 97 set in 1999.

Forecasters said it felt even hotter because of the high humidity. The ridge of high pressure that brought the broiling weather is expected to remain parked over the region through Thursday.

"I'm staying in my house. I'm going to watch TV and have a cold beer," said 84-year-old Harvey Milliman of Manchester, N.J. "You got a better idea than that, I'd love to hear it."

Youngsters sweltered in Hartford, Conn., where school would have ended for the summer by now if not for the heavy snows last winter that led to makeup days.

Public schools in Philadelphia and parts of New Jersey and Maryland cut their days short. But Baltimore students were disappointed to find a public pool closed when school let out early. The mayor later ordered the pools to open.

In Oklahoma, where temperatures have reached 104 four times so far this month, the Salvation Army said more people are seeking help with high utility bills earlier in the season, and paramedics responded to more heat-related illnesses.

The deaths of five elderly people in Tennessee, Maryland and Wisconsin have been blamed on the heat in recent days.

Cooling centers were opened in cities such as Chicago, Memphis, Tenn., and Newark, N.J., as a refuge for those without air conditioning. City officials in Norfolk, Va., teamed up with nonprofit groups to deliver cold water and sunscreen to the homeless.

And this could be just the beginning.

The 6-to-10-day outlook from the federal Climate Prediction Center calls for continued above-average readings centered on the mid-South, including Louisiana, Mississippi and Alabama, and extending as far as the Great Lakes and New York and New Jersey.

That is likely to continue in the coming month, with the hot weather extending west into New Mexico and Arizona. The three-month outlook shows excessive heat focused on Arizona and extending east along the Gulf Coast. Cooler-than-normal readings are forecast from Tennessee into the Great Lakes states.