Most of the rain is forecast to fall in as little as 3-6 hours. A small chance of heavier rain and flooding could pose "an elevated threat to life and cause significant disruptions to transportation, flood underground infrastructure and basements and first floors of residences and businesses," with water rescues needed, the weather service said.

Heavy rain triggers flash floods and travel chaos on US East Coast Severe thunderstorms brought heavy rainfall and flash flooding to the US East Coast on Thursday, grounding flights and forcing emergency rescues of stranded drivers from Philadelphia to New York City.