[BBC] – The north-eastern US states of New York, New Jersey, Pennsylvania and Virginia have declared states of emergency as a huge winter storm sweeps in, bringing heavy snow.

The US National Weather Service issued blizzard warnings from eastern Pennsylvania to south-west Maine. Schools are closed and thousands of flights have been cancelled.

The conditions caused German Chancellor Angela Merkel to postpone a trip to Washington to meet President Trump. That has now been rescheduled for Friday.

With winds of up to 60mph (100km/h), the storm is expected to cause severe disruption for commuters across many parts of the north-east. In all, about 50 million people across the country have been warned about the severe weather.

Less snow than anticipated is now expected to fall in New York City, with the forecast downgraded to between 4 and 8 inches (10-20cm) by the US National Weather Service.

However, up to two feet of snow was still expected other parts of New York state, the service said.

“During its height we could see snowfall rates of 1-3 inches (2.5-7.6cm), even up to four inches per hour,” said Alan Dunham, a meteorologist based in Taunton, Massachusetts.

More than 6,800 flights have been cancelled, tracking service FlightAware reported, with airports in New York, Washington, Boston, Baltimore and Philadelphia worst hit. Many schools have closed in New York and Rhode Island, and in some towns across Massachusetts and Connecticut.

Declaring a state of emergency, New York Governor Andrew Cuomo said commuters should expect road closures, delays and cancellations.

“I strongly urge everyone to limit unnecessary travel on Tuesday and if you must drive, please plan ahead, be careful, and stay safe,” he said in a statement.

Last night, Mr Cuomo advised New Yorkers to prepare food supplies for seven to 10 days, and an emergency supply of bottled water.

New Jersey Governor Chris Christie also declared a state of emergency and ordered all state employees not involved in the response to stay at home.

The winter storm follows a spell of unusually mild weather in the north-eastern US, with last month being the second warmest February since record-keeping began in 1895.

President Trump said he had spoken to Homeland Security and that the Federal Emergency Management Agency was ready to provide assistance where needed.

“Everybody in government is fully prepared and ready,” he said. “Let’s hope it’s not going to be as bad as some people are predicting. Usually it isn’t.”

In 2016 New York experienced the biggest snowstorm in the city’s history, with a record 27.3 inches falling on Central Park in 24 hours.

The blizzard brought parts of the north-eastern states to a standstill, and left 18 people dead.