[World] US storms: 'All hands on deck' as floods deluge US north-east

More than 13 million people in the US north-east are under flood alerts as a deadly storm that has already caused widespread damage deluges the region.

Flash flooding from excessive rainfall was expected across New England until Tuesday morning with Vermont facing the highest risk, forecasters said.

Officials warned parts of Vermont to brace for "catastrophic" flooding on a level not seen since 2011.

New York's governor has declared a state of emergency in two counties.

Flood watches issued for parts of Pennsylvania, New York, Massachusetts, Maine, New Hampshire, New Jersey and Connecticut will remain until at least Tuesday afternoon.

A woman in her 30s died in New York state as flood waters swept through streets on Sunday.

She was trying to flee her home with her dog for safety.

"She crossed with a pet and lost her footing and unfortunately was washed away down into a ravine," a New York Orange County official told NBC News.

More intense rainfall is forecast for far north-eastern New York state and parts of northern Vermont.

"Dangerous flooding in these areas are forecast to continue or worsen throughout the night, with impacts turning from flash flooding to river flooding," the National Weather Service (NWS) said on Monday.

The NWS warned much of Vermont to be on alert for "catastrophic flooding that has not been seen in this part of the country since 2011".

Flooding has already occurred in the New England state, rendering multiple areas inaccessible. US media report people being forced to travel via canoes, and churches being converted into shelters.

Crews from North Carolina, Michigan and Connecticut have joined the rescue effort in Vermont.

They are trying to reach towns like Londonderry and Weston that have been cut off by the deluge.

"This is an all-hands-on-deck response," Vermont Governor Phil Scott told a Monday press conference.

"We have not seen rainfall like this since Irene, and in some places, it will surpass even that."

In 2011 Tropical Storm Irene killed six people in Vermont.

At another news conference on Monday, New York Governor Kathy Hochul said the storm had sent "cars swirling in our streets".

"The amount of water is extraordinary," she said.

The aptly named town of Stormville, 50 miles (80 km) north-east of New York City, saw 8in (20 cm) of rain from Sunday to Monday.

Governor Hochul said people were missing and declared a state of emergency for two counties.

Homes, businesses and roads were significantly damaged in Orange County.

At the US military's West Point academy, nearly 7in of rain fell in just three hours. US media described it as a one-in-1,000 year rain event for that location.

The military academy wrote in a Facebook post on Monday that "West Point remains on Code Red".

The NWS added that the storm is not expected to leave the region entirely until late Tuesday or early Wednesday.

Meanwhile, more than 1,000 flights to New York airports were cancelled as a result of the weather.

Amtrak suspended train services between New York City and Albany after flooding damaged tracks.

Many factors contribute to flooding, but a warming atmosphere caused by climate change makes extreme rainfall more likely.

Extreme heat is forecast for the south-western US this week, including Arizona, where the NWS said conditions were "rivalling some of the worst heat waves this area has ever seen".