(NEW YORK) — Up to 100,000 people in Washington state could be ordered to evacuate amid a threat of “catastrophic” flooding from an atmospheric river event, officials said.

Washington Gov. Bob Ferguson, who announced a state of emergency on Wednesday, pleaded with residents to follow evacuation orders and warned on social media, “Catastrophic flooding is likely.”

In Skagit County, north of Seattle, officials called for evacuations amid the major flooding, saying “residents within the FEMA 100-year floodplain need to evacuate to high ground immediately.”

Multiple rivers are at major flood stage and more are expected to grow into major flood stage later in the day on Thursday.

The Snohomish River at Snohomish reached a record high of 33.9 feet on Thursday morning, and it may stay near this level for 24 hours. The floodwaters are expected inundate much of the river valley and could overtop the levees.

Record flooding is possible at other river locations, including the Skagit River near Concrete and near Mount Vernon, the Snoqualmie River at Snoqualmie Falls, the Cedar River at Renton, and the Snohomish River near Snohomish Monroe.

Washington Sen. Maria Cantwell said on social media she was “alarmed” to hear the Skagit River could peak as high as 5 feet above its record crest level.

“Please please please stay alert and follow evacuation orders,” she posted. “This is not just another flood.”

Roads are flooded and closed across North Bend — a city about 30 miles east of Seattle — and mudslides have closed parts of Interstate 90.

Eastside Fire and Rescue, which services parts of King County just east of Seattle, started conducting water rescues on Wednesday. Three adults and a dog were rescued after their home flooded, and two adults and a child were rescued in another incident.

Eastside Fire and Rescue released video of the moment two drivers were rescued rescued by helicopter Wednesday night. After the drivers were caught in the floodwaters, they were forced to flee to higher ground, with one person climbing to the top of their car and the other seeking safety in a tree, officials said.

“Stay home and don’t travel unless necessary,” the sheriff’s office urged on Thursday.

The flooding was sparked by an atmospheric river event that dumped more than 1 foot of rain at higher elevations of western Washington state over the last three days. The heavy rain is continuing Thursday morning and then will weaken throughout the day.

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