Tens of thousands of people in the US state of Washington were ordered to evacuate on Thursday evening amid surging floodwaters that have inundated farmland.

At least 78,000 people in the state's agricultural region were told to flee the floodplain, one day after the state declared a state of emergency.

Over 12,000 homes were without electricity on Thursday night, according to PowerOutage.us.

The northwest of the United States has seen torrential rainfall in the past few days due to a weather phenomenon called atmospheric river, in which a band of extremely moist air delivers intense rainfall for days. 

Washington governor warns of 'potentially historic' floods 

"The flooding levels we're looking at are potentially historic in nature, so we just want to emphasize how serious the situation is," Governor Bob Ferguson said at a news briefing Thursday.

He said more than 30 major highways had been closed due to traffic.

On Friday, Pierce County's fire department posted a video of emergency crews rescuing stranded residents in the city of Puyallup.

"Turn around, don't drown. Never drive through flooded roads. Stay out of floodwaters. They can hide debris, other hazards, and have strong currents," they said, advising people to follow evacuation orders. 

National Guard deployed to rescue people from flooding

The local county website warned of possible mudslides, flooded roads and broken river banks.

"While the rains have slowed down, many rivers and creeks across Pierce County remain at elevated flood Levels," one advisory said.

Meanwhile, the National Guard has been deployed with helicopters and boats being used to bring people to safety.

Along the river in Mount Vernon, teams knocked on doors in low-lying areas to inform them of evacuation notices, city authorities said.

Edited by: Karl Sexton