Heat wave descends on the US

9:13 a.m. ET, July 19, 2019

New York City has declared a local emergency over the heat

New York City Mayor Bill de Blasio has declared "a local emergency due to the extreme heat" in New York City.

The executive order covers 9 a.m. Friday to 11:59 p.m. Sunday, and the mayor is ordering buildings 100 feet or taller to raise thermostats to 78 degrees in an effort to conserve energy.

"We are about to enter a heat emergency, and must do all we can to keep New Yorkers safe," said de Blasio. "The city government is limiting its energy use to reduce strain on the electrical grid, and now private office buildings will also have to do their part."