Flash Flood Alerts: 40M at Risk in NYC, Northeast States

A significant storm system moving across the eastern United States is expected to bring torrential rain, flash flooding, and severe thunderstorms to parts of the Northeast and Mid-Atlantic through early Friday morning, while cooler and less humid air from Canada promises relief heading into the weekend, according to AccuWeather meteorologists.

Flash flood risk zones: Over 40 million affected

According to AccuWeather, a “one-two punch” of an approaching cold front and a jet stream disturbance is expected to produce a swath of heavy rain from eastern Pennsylvania, eastern Maryland, far northern Virginia, and northern Delaware, northward through the lower Hudson Valley of New York, including New York City, and into Connecticut, Rhode Island, and parts of Massachusetts.

This region—home to approximately 43 million people—may receive 2 to 4 inches of rain, with localized amounts up to 8 inches, according to the weather agency's forecast. Rainfall at this intensity could overwhelm storm drains and cause urban flash flooding, disrupt travel on highways like Interstate 95, and lead to subway flooding in major cities like New York.

Rainfall of this magnitude can result in rapid rises on small streams and significant runoff in poorly drained areas, AccuWeather warned.

Severe storms from Pennsylvania to South Carolina

AccuWeather also forecasts severe thunderstorms with damaging wind gusts and localized flooding Thursday across a stretch from southern Pennsylvania and southern New Jersey, down through Delaware, Virginia, North Carolina, and into South Carolina.

Although storms with flash flood potential will be scattered throughout this region, the greatest rainfall concentration is expected across the northern tier of the storm zone, especially into Thursday evening, AccuWeather said.

By Friday, isolated strong storms may reach farther south along the Atlantic coast, including southern Georgia.