San Francisco Frontiers - Dangerous heat wave roasts America's big birthday party

Around 160 million Americans were under either major or extreme heat warnings as the country prepared to mark the 250th anniversary of its independence, according to the National Weather Service.

Celebrations on the National Mall -- the vast lawn stretching from Congress to the Washington Monument -- -- were partially postponed in the early afternoon on Friday because of the heat.

A young woman apparently suffered from heat exhaustion and was evacuated by paramedics from the Great American State Fair, being held on the Mall.

"It's like the 30th person," said an event staffer. "They might have to shut this (event) down."

Less than 90 minutes later, organizers did just that.

In New York City, the heat index -- the apparent temperature when humidity is factored in -- stood at 105F (41C) in mid-afternoon, shy of the 115F that forecasters had predicted.

Still, the brutal heat prompted a massive governmental response, with cooling centers opening across the city and public swimming pools extending hours of operation.

Across the country, "numerous daily temperature records are expected today and Independence Day, with some consecutive-day, monthly, and all-time records possible," the National Weather Service said.

- Heated celebrations -

Early on Friday, Hang Dang, a 76-year-old retiree, said she was not letting extreme temperatures keep her from attending July 4th celebrations in Washington.

"I came to the US in 1975 from Vietnam and... I was here for the bicentennial," Dang told AFP, noting she drove 12 hours from Florida to attend festivities.

"I said I've got to get back for the 250th because I don't think I'll make it to the 300th!" she joked as a Marine Corps Osprey aircraft hovered nearby.

Around midday lines to enter the state fair appeared to be more than 400 ft (135m) long as temperatures climbed towards a forecast high of 102F.

Inside the festival, attendees sheltered in the short midday shadows cast by the temporary buildings set up for the event.

Standing outside one pavilion, a woman repeatedly shouted, "Homeland Security, here! Spin the wheel, win a prize! Full blast A/C in there!" as she pointed to the door.

Around an hour later, a voice over the public address system rang out: "Attention fair-goers, the event has been postponed. We will re-open at 5pm...Please proceed to the nearest exit."

- Scorching matches -

In Miami -- a city that is no stranger to heat -- Argentina and Cape Verde were slated to face off at 6pm in a stadium that has a partial roof canopy but no air conditioning. The forecast heat index for the 6pm kickoff was 100F.

On Saturday, France and Paraguay will clash in Philadelphia, where the heat index could reach 105F.

Due to the heat FIFA has introduced a mandatory "hydration break" in each half of every game at this World Cup, although it was not clear whether that would be adequate for matches taking place outdoors during the heat wave.

- Stressed grids -

Preliminary data showed the daily heat record in the US capital was likely broken when the nearby airport reached 102F, pipping the previous July 3 record from 1966 when the mercury reached 101F.

The intense heat and related air conditioner usage was stressing electricity grids across the country.

New York's utility provider, Con Edison, said that its crews restored electricity to some 60,000 residents after heatwave-driven outtages.

More than 22,000 people were without power around 4:30 pm (2030 GMT) on Friday across New York City and some suburbs.

PJM, the company that coordinates multiple grids on the East Coast and parts of the Midwest that serve 67 million customers, said it was considered asking data centers to switch to emergency back up power Thursday to relieve grids, among other actions. While that call was not made, the company said it was an option on the table for Friday.

bur-pnb/dw

H.Reyes--SFF