A brief but intense heat wave set or tied several records across the Northeast and mid-Atlantic on Wednesday.
Baltimore and Washington hit 99 degrees, breaking high-temperature records for a June 8 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.
It felt even hotter with high humidity and a ridge of high pressure parked over the East Coast and Southeast states through Thursday.
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.
"I'm not even going to go outside this summer if it's going to be like this, unless my mom makes me," said seventh-grader Kemeshon Scott, putting the final touches on a social studies paper in a Hartford school with no air conditioning.
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 official arrival of summer is still about two weeks away.
The deaths of five elderly people in Tennessee, Maryland and Wisconsin have been attributed to high temperatures in recent days, and public schools in Philadelphia and parts of New Jersey cut their school days short Wednesday to limit the amount of time students spent in buildings with no air conditioning.
Heat advisories and warnings were issued for New York City, Philadelphia and the Baltimore-Washington region on Wednesday. Heat advisories also were issued for parts of Ohio, Indiana and Michigan.
Air quality alerts also were issued across the region, including in New Jersey. Officials said ozone levels could cause problems for children, the elderly and those with respiratory problems. The state's Health Department said men ages 65 to 84 years of age are the largest group hospitalized for heat exposure each year.
Public schools in Philadelphia and parts of New Jersey cut their school days short in response to rising temperatures.
In the District of Columbia, trash collection will begin an hour earlier than normal because of the extremely hot weather forecast. City officials warned residents not to open fire hydrants to cool off because it reduces water pressure and hampers firefighting.
Buckled highways in Minneapolis
As the heat wave has pushed east, it has crushed previous record highs in St. Louis and St. Paul, Minn., where the mercury reached 102 degrees on Tuesday and finally melted a giant snow pile in a Sear's store parking lot.
The heat and humidity has been so high this week in the Minneapolis-St. Paul area that 28 pavement failures, or buckled roads, were reported Monday afternoon on highways, causing traffic snarls.
"I don't remember having seen as many as this in one afternoon," said T. K. Kramascz, spokesman for the Minnesota Department of Transportation.
Cities like St. Louis and Detroit have cooling centers for overheated residents. Cincinnati's fire department sent out extra personnel on calls, so commanders could rotate out exhausted teams.
And in Chicago, some public school students struggled to concentrate on finals in non-air-conditioned classrooms as the outside temperature approached a record 97 degrees.
Chicago school principals were told to keep students hydrated and move classes if necessary from rooms exposed to sunlight, according to guidelines distributed to schools. Principals may relax dress codes and allow students to wear shorts, the guidelines said.
"It's perspiratory and sweltering," said AccuWeather.com meteorologist Elliot Abrams. "You take a shower and step outside and the sweat beads form almost immediately."
Abrams warned that people who work outside have to watch out for possible over-exertion and heat stroke.
Jim Allsopp, a meteorologist for the National Weather Service, said temperatures in Illinois were running "well above normal" by about 15 degrees.
He said "very warm air" came into the area from the southwest.
The heat wave, which led to schools dismissing students early and sports events being rescheduled, started over Sunday with heat advisories stretching from Tennessee down through Mississippi and Louisiana.
"It typically doesn't get this hot this quickly," said National Weather Service meteorologist John Cohen in Nashville. "Normally you get into July and August before you'll have a time period where you have temperatures well into the 90s like we're having day after day after day."
Affected cities include St. Louis, which saw a record 97 degrees on Monday.
By Tuesday, 43 cooling centers were open in the St. Louis area to help residents beat the heat. Since Saturday, emergency workers have responded to 12 heat-related cases, the St. Louis Department of Health reported.
Less than two months ago, a tornado hit St. Louis, destroying nearly 100 homes and damaging the Lambert-St. Louis International Airport.
By Friday, the northern half of the U.S. should see a cold front come in to reduce temperatures. Minneapolis, for example, should be back down into the 60s after Tuesday's 102 — the warmest day there since 1988, according to the Minneapolis Star-Tribune.
The cold front is expected to head to the Northeast by Friday, weather.com reported, bringing the possibility of clouds, showers and thunderstorms that will help lower temperatures.