(NEW YORK) -- Intense heat has returned to the Northeast, with 70 million Americans facing heat advisories on Thursday that will likely extend into the weekend.
Boston is projected to reach 99 degrees on Thursday, breaking a 96-degree high from 1928, according to the National Weather Service. The mayor of Boston declared a heat emergency on Wednesday through Sunday, opening 16 cooling centers across the city.
"I urge everyone to stay cool and safe, and check on your neighbors during the week," Mayor Michelle Wu said in a statement.
Hartford, Connecticut, is forecast to hit 101 degrees on Thursday, breaking a 1944 record of 96 degrees, the NWS said.
Newark, New Jersey, could tie a 1993 record of 100 degrees. The city of Newark issued a Code Red on Wednesday, urging residents to take precautions against the dangerous heat.
New York City is forecast to break a 2006 record, reaching 94 degrees on Thursday, according to the NWS.
Con Edison, the city's energy supplier, issued an advisory on Wednesday, asking residents to conserve energy due to the anticipated heat and humidity creating increased demand for electricity.
Philadelphia is expected to tie a 1995 heat record by reaching 95 degrees, according to the NWS.
Two heat deaths have been reported in the Northeast over the last two weeks, one in New York City and one in Philadelphia, officials said. Authorities have warned residents of the danger for more fatalities.
The heat will peak on Thursday, will highs forecast to decrease slightly on Friday before rising again on Sunday. The NWS predicts thunderstorms across the Northeast over the weekend, as heat and humidity come to a head.
The dangerous heat has persisted throughout the summer, with records broken across the Northeast just two weeks ago being threatened once again.
Last week, a heat wave settled over the Northwest, where over a dozen deaths have now been linked to the extreme temperatures.