A state of emergency has been declared in New York City and New Jersey as a powerful storm system is bringing torrential rain and flash flooding to a swathe of the US east coast from NYC to Washington DC.

Forecasters are predicting intense rainfall, with rates possibly reaching up to 3 inches an hour. While most areas are expected to receive 1 to 3 inches of rain, certain isolated locations could see as much as 5 to 8 inches.

Kathy Hochul, the New York governor, said she would be declaring a state of emergency for New York City and the surrounding counties. In a post on X, she said: “Heavy rain and potential flooding are expected to affect the evening commute. Employers are encouraged to dismiss employees early. Continue to monitor your local forecasts, and stay safe.”

In anticipation of the severe weather, the acting New Jersey governor, Tahesha Way, had earlier declared a state of emergency for the state, effective from 2pm on Thursday. The declarations come amid concerns over flooding, strong thunderstorms, heavy rainfall and gusty winds.

“Beginning this afternoon, we are expecting severe thunderstorms to bring heavy rainfall and damaging wind gusts with the potential for flash flooding across the state,” said Way. “I urge all New Jerseyans to remain alert, follow all safety protocols, and monitor the proper channels for the duration of these storms. Residents should remain off the roads and indoors unless absolutely necessary.”

The combination of saturated ground and intense downpours raises the risk of hazardous conditions such as flash floods, rock slides, and landslides. Officials warn that travel could become dangerous, especially during the evening commute, when the heaviest rain is expected.

Storm activity began early afternoon and could continue well into the night.

New York City also issued a travel advisory for both Thursday and Friday. A flood watch will go into effect on Thursday afternoon.

“Be prepared for a serious storm,” the mayor, Eric Adams, said in a social media post. “Avoid traveling if you can, and set up any flood prevention tools in advance,” he added.

Zachary Iscol, commissioner of New York City Emergency Management (NYCEM), also warned those in the area that the storm system “could bring intense rainfall rates and amounts in a very short period of time”. He added that the NYCEM has already activated the flash flood emergency plan.

The warnings come just two weeks after intense rain storms hit parts of the northeastern US, flooding New York City subways and resulting in two deaths in New Jersey.