Intense downpours were swept into the region this week by an ‘atmospheric river’ storm system from the Pacific Ocean.

Intense rains that triggered “catastrophic flooding” in North America’s Pacific Northwest have finally eased, though meteorologists warn the effects of overflowing rivers and floodwaters will continue to be felt for several days.

Tens of thousands of people were told to evacuate on Thursday across the US states of Oregon and Washington, up through the Canadian province of British Columbia, after rainstorms battered the region for several days, causing rivers to burst their banks.

Western Washington state has borne the greatest brunt of the storm, with roughly 100,000 residents under “Level 3” evacuation orders.

State authorities have ordered people living south of the cities of Seattle and Tacoma to leave their homes, with aerial photographs showing farmland already under water, and populated areas perilously close.

In the city of Orting, south of Seattle, authorities warned there is a “significant threat to life and or property”.

There have been no reports of casualties or missing people due to the flooding, according to Karina Shagren, spokesperson for Washington’s emergency management division.

Across the border in British Columbia, swaths of the Canadian city of Abbotsford, east of Vancouver, were swamped as of Thursday night, with hundreds of properties at risk.

Five of the six highways leading in and out of Vancouver were also closed due to floods, falling rocks and the risk of avalanches, the province’s Ministry of Transport said, describing the situation as “evolving and very dynamic”.

The main highway route between Vancouver and Seattle remains open.

The intense downpours were swept into the Pacific Northwest region earlier this week by an atmospheric river, a vast airborne current of dense moisture funnelled inland from the Pacific Ocean.

The storm system, which dumped more than 250mm (10 inches) of rain in some places, also brought heavy showers and flooding as far away as western Montana and the edge of northern Idaho.

Though the downpour began to lessen on Thursday, the after-effects are expected to linger across the region as high volumes of water make their way through swollen river systems.

“While drier weather looks to be in store for this area of the country through the upcoming weekend, the major … catastrophic flooding effects are likely to continue for several days across portions of western Washington State and northwestern Oregon,” the US National Weather Service said.

The National Water Center has issued an updated Key Messages for the ongoing Catastrophic flooding impacts this week in Washington. More info: https://t.co/UZ3ekqUUkq #flooding #wawx pic.twitter.com/KwdS8a9T5y

— National Water Center (@nwsnwc) December 11, 2025