More than 60 million people from Ohio to Massachusetts to Virginia are bracing for possible flash flooding on Monday after a deadly holiday weekend heat wave left much of the East Coast sweltering in triple-digit temperatures.
New York and Long Island appear to be in the center of the storm, with a flash flood threat level of 3 out of 4. Southern Connecticut, Rhode Island and southeastern Massachusetts are also expected to see heavy rain.
Up to 3 inches of rain per hour is possible in some parts of the Northeast, with up to 8 inches possible in some areas.
A thunderstorm moves across the Hudson River into lower Manhattan in New York City on July 3, 2026.
Gary Hershorn/ABC News
A flood watch will be in effect for all of New York City until Monday evening. A flash flood warning was issued Monday for the New York City boroughs of Brooklyn and Queens, where 1 to 2 inches of rain had already fallen Monday morning.
A flash flood warning was also issued for more than 2.5 million people in the Philadelphia area where flooding had already been reported Monday, including in the Lemon Hill Park neighborhood of North Philadelphia.
New York City Mayor Zohran Mamdani issued an online video statement on Sunday advising New Yorkers to take precautions.
Flash flood threat, July 6, 2026
ABC News
“We ask New Yorkers to stay safe, stay prepared and look out for each other during this time,” Mamdani said, adding that city workers were out over the weekend clearing watersheds and preparing areas that have historically been prone to flooding for the approaching storm.
The mayor asked New Yorkers living in basement apartments to plan to evacuate.
Lightning strikes the World Trade Center during a thunderstorm in New York City on July 3, 2026.
Gary Hershorn/ABC News
“If you see water rising around you, move to higher ground,” Mamdani said.
In Ocean Township, New Jersey, severe weather may have caused the roof of BJ’s Wholesale Club to partially collapse while 27 people were inside the store, according to Monmouth County Sheriff Michael Sorrentino.
Sorrentino said the incident occurred around 11:16 a.m. He said two people were partially pinned but managed to free themselves and exit the premises safely. According to him, no injuries were reported.
“This incident is another reminder of how quickly severe weather can create dangerous and unpredictable conditions,” Sorrentino said in a statement.
Flood warnings, 6 July 2026
ABC News
Meanwhile, as of 2:30 p.m. ET, more than 700 flights were canceled at New York and New Jersey airports due to severe weather conditions.
All major airports in the New York region reported flight delays of more than an hour due to the thunderstorm, with the Federal Aviation Administration issuing ground stops throughout the day.
Flights from Ronald Reagan Washington National Airport and Philadelphia International Airport were also delayed due to the thunderstorm.
The storms expected on Monday follow a multi-day heat wave. Parts of the Mid-Atlantic and South received heavy rain Sunday night.
At one point, more than 800,000 utility customers from Oklahoma to Connecticut lost power Sunday, including 85,000 in New York, according to PowerOutage.com.
New Jersey Gov. Mickey Sherrill said thunderstorms Friday night and over the weekend knocked out power to nearly 300,000 utility customers and brought down trees and power lines with wind gusts of up to 80 mph.
At least 25 people are believed to have died in New Jersey as sweltering heat gripped much of the country, officials said.
At least 60,424 utility customers in New Jersey, 43,664 in New York, more than 95,000 in Pennsylvania and at least 100,000 in Michigan were without power Monday morning, according to PowerOutage.com.
New Jersey Health Commissioner Dr. Raynard Washington told reporters at a news conference Saturday that many of the people who died from the heat in New Jersey were found in homes without air conditioning.