The National Weather Service has issued a severe thunderstorm warning for much of the Northeast (National Weather Service) warned that damaging winds, hail and frequent lightning are possible through 11 p.m. ET Saturday.
The monitoring covers parts of Delaware, Maryland, New Jersey, New York and Pennsylvania, affecting more than 21 million people.
The Storm Prediction Center (SPC) said scattered severe thunderstorms are expected in the afternoon and evening. The most intense storms could produce wind gusts of up to 75 mph.
Areas under severe thunderstorm warning
The watch covers parts of five states, including major metropolitan areas and surrounding counties, according to the National Weather Service. Cities in or near the surveillance area include New York City, Philadelphia, Allentown, Scranton, Harrisburg, Binghamton, Poughkeepsie, Atlantic City, Salisbury, Rochester and Syracuse.
Severe storms are most likely in the Philadelphia metro area and south.
The storm group will continue through the Allegheny Plateau region and into the mid-Atlantic, bringing the risk of multiple damaging winds. Additional severe thunderstorms are possible across the Plains this afternoon and evening, bringing the risk of strong wind gusts and large hail.
Forecasters noted that damaging straight-line winds remained a major concern. Such winds can knock down trees, damage roofs and power lines, and cause localized power outages.
Frequent lightning may also pose risks to people attending outdoor events or fireworks displays. Officials urged residents to monitor weather warnings and seek sturdy shelter in the event of a storm.
Also read: Extreme heat wave disrupts July 4th and East Coast U.S. 250 races
Fourth of July flash flood threat
In addition to strong winds, forecasters warned that slow-moving thunderstorms could produce heavy rainfall that could lead to localized flash flooding. according to National Weather Servicethunderstorms may produce 1 to 2 inches of rain per hour, especially in urban and poorly drained areas.
The period of greatest concern is expected at 2 a.m. Sunday, when recurring thunderstorms could flood storm drains and flood roads. Officials advise drivers not to travel through flooded roads because it is difficult to judge the depth of the water at night.
Outdoor Fourth of July celebrations, fireworks displays and sporting events could be disrupted if thunderstorms move through affected communities. Emergency managers urged residents to move indoors immediately after hearing thunder.
The extreme heat warning will cease at 8pm tonight, but dangerous temperatures will continue on Sunday, with heat index values ​​reaching 95°-100° in some areas.