The extent of the damage in Washington state is profound but unclear after more than a week of heavy rains and record flooding, according to the state’s governor, Bob Ferguson.

A barrage of storms from weather systems stretching across the Pacific has dumped close to 2ft (0.6 metres) of rain in parts of the state, swelling rivers far beyond their banks and prompting more than 600 rescues across 10 counties.

More high water, mudslides and power outages were in the forecast. Elevated rivers and flood risk could persist until at least late this month, according to the National Weather Service. Wind and flood watches and warnings are expected in much of the north-west for the next couple of days as storms bring rain, heavy mountain snow and high winds.

As of Tuesday, authorities had recorded one death – of a man who drove past warning signs into a flooded area – but key highways were buried or washed out, entire communities had been inundated, and saturated levees had given way. It could be months before State Route 2, which connects cities in western Washington with the Stevens Pass ski area and the faux Bavarian tourist town of Leavenworth across the mountains, can be reopened, Ferguson said.

“We’re in for the long haul,” Ferguson said at a news conference. “If you get an evacuation order, for God’s sakes, follow it.”

It won’t be until after waters recede and landslide risk subsides that crews will be able to fully assess the damage, he said. The state and some counties are making several million dollars available to help people pay for hotels, groceries and other necessities, pending more extensive federal assistance that Ferguson and Washington’s congressional delegation expect to see approved.

According to the governor’s office, first responders had conducted at least 629 rescues and 572 assisted evacuations. As many as 100,000 people had been under evacuation orders at times, many of them in the flood plain of the Skagit River north of Seattle.