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.
