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.

States of emergencies were declared in New York City and New Jersey as torrential rain pounded the Northeast on Thursday afternoon. A level 3 out of 4 threat for flash flooding was in effect in New York City,