More than 800,000 customers from Oklahoma to Connecticut remained without electricity on Sunday as more severe storms were expected to bear down across parts of the southern and eastern United States, bringing the threat of powerful winds and flooding rains.

A majority of the power failures were in Michigan, Pennsylvania and New York on Sunday, according to PowerOutage.com, a tracking site.

In New York, there were about 85,000 customers without power.

In New York City, Mayor Zohran Mamdani warned on social media about the high temperatures as the World Cup match between Brazil and Norway was scheduled in New Jersey for Sunday afternoon.

“These past few days have been scorching, back-to-back 100-degree days, brutal humidity,” he said, adding that cooling centers in the city were open.

Chris Hoenig, a spokesman for Jersey Central Power and Light, said on Sunday that the company had restored power to 210,000 of the 294,000 customers in New Jersey who lost service between Friday and Saturday because of severe weather.

“The vast majority of the remaining customers will have their power restored over the next three days,” he said.

In Connecticut, more than 68,000 customers were left without electricity.

“It was bad,” said Elizabeth Meduna, 54, who lives in Tolland, Conn., north of where the storms struck on Saturday night.

“I thought the thunder was fireworks,” she added. “The hail was incredible.”

In Michigan, more than 222,000 customers were without power on Sunday. One of the state’s largest utilities, DTE Energy, said that more than 85 percent of its affected customers would have their power restored by the end of Sunday.

The threat of severe weather was expected to continue on Sunday, mainly in the Mid-Atlantic and Texas.

The Storm Prediction Center said the primary threat in both regions was for damaging wind gusts, although some of the storms in Texas could also produce hail. Frequent lightning was also expected.

In Texas, the highest concentration of storms was expected in the western and northwestern parts of the state, including areas near Lubbock on Sunday afternoon.

In the Mid-Atlantic, storms were forecast to develop on Sunday afternoon and into the evening, with the greatest threat for stronger wind gusts across parts of Delaware, New Jersey, Maryland, Pennsylvania and northern Virginia, including the cities of Arlington, Va., Baltimore, Philadelphia and Washington, the center said.

An additional concern was the risk of flash flooding, particularly in parts of the Northeast.

The Weather Prediction Center said that storms could repeatedly move over the same areas, leading to high rainfall rates of more than two inches per hour in some locations.

The highest risk of localized flash flooding on Sunday was expected across eastern Pennsylvania and northern New Jersey.

Flood watches were in effect through late Tuesday for parts of the Northeast, including Boston, southern New York (including Long Island), northern New Jersey and central to southeastern Pennsylvania.

From Monday forward, forecasters said the main storm system would gradually weaken and move away but scattered showers and thunderstorms could still develop across parts of the Mid-Atlantic that afternoon, especially in Virginia and North Carolina.