Severe storms threaten East Coast after July Fourth disruptions

More than 501,000 utility customers remained without power Monday morning, with the heaviest outages in Pennsylvania and Michigan, as severe storms threatened the East Coast with more flooding, damaging wind and hail after July Fourth celebrations were disrupted by rain, lightning and heat.

CBS News' flood-watch estimate put 34 million people in the Northeast under a flood watch through late Monday, with Philadelphia and New York City facing up to four inches of rain between Monday and Tuesday. Strong to severe thunderstorms were possible from the mid-Atlantic into the northern Plains, and isolated tornadoes were possible in the Plains, although wind gusts and hail were expected to be the main threats.

In New Jersey, state health officials reported at least 25 suspected heat-related deaths as extreme heat overlapped with the storm outbreak.

In Washington, D.C., thunderstorms forced the temporary evacuation of thousands from the National Mall. More than 10,000 attendees were told to seek shelter in nearby buildings as storms moved in. The Freedom 250 celebration there included a delayed address from President Trump and a fireworks show.

The National Weather Service put more than 185 million people under heat alerts Friday, and peak heat indexes could climb to 115 degrees in some places. AccuWeather counted more than 2,000 reports of severe weather across the Plains and East Coast since the beginning of July, with nearly 1,000 incidents on July Fourth alone.

In New York City, officials deployed vans staffed with nurses and paramedics to hand out water, electrolytes and sunscreen, perform wellness checks and transport residents to cooling centers.