Americans withered under yet another day of searing sun Friday as a heat wave spread in earnest into the urban core of the Northeast, while warnings about excessive heat stretched from Kansas to Maine and the Carolinas. The extreme heat extended north into Canada in communities across southern Ontario and Quebec.

Temperatures hit 100 degrees Fahrenheit (38 degrees Celsius) in New York's Central Park and in Newark and Teterboro, New Jersey. The National Weather Service said the smoldering humidity made those temperatures feel like 116 Fahrenheit (47 C), 114 Ft (46 C) and 110 Ft (43 C) , respectively.

In Canada, an extreme heat alert remained in effect Friday in several Canadian cities, a day after at least 17 cities and towns in Ontario and Quebec broke their previous single-day records for July 21, Environment Canada said. In Toronto, Canada's most populous city, the temperature set a single-day record of 100.2 degrees Fahrenheit (38 degrees Celsius) on Thursday, and forecasters said the the high should reach 95 F (35 C) on Friday.

Across the U.S., emergency room visits were way up, according to public health officials, mainly because of people suffering from heat exhaustion and heat stroke.

The weather is suspected of contributing to a number of deaths nationwide. At least six more fatalities were reported Thursday, including a Michigan restaurant cook who suffered a heart attack after being sent home from his job and a teenage boy who drowned while swimming at a summer camp in the same state.

In New York, people looking to beat the heat also were thwarted by warnings urging them to avoid some city waterways after a wastewater treatment plant disabled by fire began spewing millions of gallons of raw sewage into the Hudson River.

Officials cautioned against swimming and bathing at four beaches in the city boroughs of Staten Island and Brooklyn, especially for people with medical conditions.

In Chicago on Thursday night, hundreds of children and more than a few adults cavorted in a shallow pool of the Crown Fountain in Chicago's Millennium Park. Temperatures hovered around 90 degrees F (32 degrees Celsius) in the park, about a half mile (800 meters) from the shores of Lake Michigan.

Christopher and Renee Mickles said they came out in the evening to give their 3-year-old a little exercise after being cooped up in their air conditioned house.

"It didn't cool off, but at least the sun isn't out," he said.

A Pittsburgh man working on the roof of his cousin's home Thursday found himself stuck for nearly two hours because of the hot tar he'd been using. Lamont Robinson said the slick tar kept him from climbing to safety after he slipped. He said he was "baking like a turkey" before his rescue. Temperatures were in the low-90s F (low 30s Celsius).

In Connecticut, a dozen Girl Scouts were treated for heat-related problems at a scout camp.

None of the girls required hospitalization, but New Fairfield First Selectman John Hodge said they spent Thursday night in the camp's cafeteria after workers brought in industrial fans to help cool them off.

Philadelphia's public schools canceled summer classes Thursday and Friday, while Allentown to the north waived fees at its public pools.

All of New Jersey, save for a sliver of its shoreline, was under an excessive heat warning. The heat forced Monmouth Park to cancel its horse racing card and reschedule it for Monday, and some businesses were planning to shut down early on Friday.

"So far, so good," said Mary Goepferd, the external affairs officer for the state's Office of Emergency Management. "We're not hearing of many major problems, and people seem to be finding ways to cope with the heat. We're also thankful that senior centers and libraries have been welcoming people who don't have air conditioning."

The heat didn't deter the hundreds of people who lined up outside the Izod Center on Friday morning to audition for NBC's singing competition "The Voice." Temperatures were already in the 80s F (upper 20s Celsius) when doors at the East Rutherford center in New Jersey opened at 7 a.m.

In Canada, the extreme heat led the Toronto Blue Jays to close the Rogers Centre's dome during their Thursday afternoon baseball game against the Seattle Mariners. Several outdoor concerts were canceled, along with horse races in a few racing tracks across the country.

And there was little respite for Canadians overnight Thursday. Several cities in southern Ontario recorded their hottest nights ever. In Toronto, the coolest it got overnight was 79.8 Fahrenheit (26.56 Celsius) at 5 a.m. EDT. The previous record for the hottest night was Aug. 1, 2006, when the lowest overnight temperature was 79.34 Ft (26.3 C).

"It was roughly 98 degrees (36 C) in my apartment last night, which makes you feel like you just took a handful of barbiturates and can barely function," said Toronto resident Briony Smith. "I took to the public pool at 9:30 last night just to get some relief."

Special dangers can come at night, experts warn, if the temperatures don't cool enough to provide relief.

While the current heat wave has recorded 12 all-time daily highs in the U.S. so far this month, it also has registered 98 all-time overnight highs, the National Oceanic and Atmospheric Administration reported at a briefing Thursday.

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Associated Press writers Randolph E. Schmid in Washington, John Seewer in Toledo, Herb McCann in Chicago, Karen Matthews in New York City and Jeff McMillan in Philadelphia contributed to this report.