The deluge set a record in Portland, which saw 2.75 inches of rain on Monday, setting a daily record, CNN affiliate KOIN said.
Also in Portland, a fallen tree trapped a 60-year-old woman in her bed on Wednesday, killing her, Lt. Rich Tyler with Portland Fire and Rescue told Oregonlive.com
And in Clatskanie, a woman drowned Wednesday after the car she was in drove into high water, CNN affiliate KOIN reported,
citing a fire official. A man who was also in the car escaped through its sunroof.
As the weather forecast predicted a steady stream of rainfall to come in off the Pacific for the rest of the week, Oregon Gov. Kate Brown declared a state of emergency in a dozen counties.
"Heavy rains and wind have required the evacuation of residences, and mudslides and high water have severely damaged or blocked major roadways in these areas of the state," Gov. Brown said late Thursday.
In neighboring Washington state, where streets and homes were flooded, and landslides closed some highways, Gov. Jay Inslee declared a state of emergency on Wednesday.
Early Thursday, a twister tore through an area near Battle Ground, Washington, close to the state line with Oregon, the National Weather Service said. Tornadoes are most common in the U.S. midsection from Texas to roughly Minnesota, and they are also common in the Deep South.
But in the Northwest and upper Northeast of the country, they are rare, the weather service has said.
The tornado was measured as an E-F1, a relatively weak reading for a tornado on the Enhanced Fujita
scale. Its maximum winds measured 104 mph.
It touched down twice, damaging dozens of homes and two businesses, but did not tear off roofs. Dozens of stout trees were uprooted or snapped.
15 inches rain
On Tuesday and Wednesday, 15 inches of rain flooded several areas of the Oregon coast, and residents in Tillamook couldn't cross a bridge to get to work, CNN affiliate KPTV reported.
"It's nuts. Just trying to get out of my neighborhood was bad," Adam Goldsborough told the station.
The Nehalem River crested at 23 feet Wednesday morning, the fourth worst recorded levels of the river in its history, officials told the news outlet.
The Wilson River crested at 20 feet, the highest it's been since 2006, threatening an RV park.
"We had to move. We moved our trailer at 9 last night, got to bed at 10. I'm guessing this is going to be the second or third worst flood here over the years. A lot of people are comparing it to '96," Vicki Tarpley told KPTV on Wednesday.