Governor Kate Brown said dozens of people are still missing and tens of thousands have been forced to flee their homes.
The state’s emergency management director, Andrew Phelps, said officials are “preparing for a mass fatality event” and thousands of structures have been destroyed.
Oregon officials have not released an exact death count but at least eight fatalities have been reported.
Marion County sheriff Joe Kast said on Friday evening that searchers had found two victims of the Beachie Creek fire near Salem.
A one-year-old boy was killed in wildfires in Washington.
Hundreds of firefighters are battling two large blazes that threatened to merge near the most populated part of Oregon, including the suburbs of Portland.
Ms Brown said more than 40,000 Oregonians have been evacuated and about 500,000 are in different levels of evacuation zones, either having been told to leave or to prepare to do so.
She dialled back a statement late on Thursday from the state Office of Emergency Management that claimed half a million people had been ordered to evacuate state-wide.
Scores of people are missing in Jackson County in the southern area of the state and in Marion County east of Salem, the state capital, Ms Brown told a news conference.
Authorities also announced that a man had been arrested on two counts of arson in connection with a fire in southern Oregon.
Improved weather has helped efforts on the ground after days of high winds, heat and low humidity.
“The wind laid down quite a bit for us yesterday,” said Stefan Myers of the state’s fire information team.
Almost 500 personnel were working on the fires near Portland, which were just a few miles apart, with rugged terrain between them that limits boots-on-the-ground efforts to control the flames, Mr Myers said.
If the fires merge, they could generate enough heat to send embers thousands of feet into the air, potentially igniting other areas.
Authorities say more than 1,500 square miles have burned in Oregon during recent days, nearly double the amount in a typical year and an area larger than Rhode Island.
Washington governor Jay Inslee noted that the amount of land burned in just the past five days amounted to the state’s second-worst fire season, after 2015. He called the blazes “climate fires” rather than wildfires.
“This is not an act of God,” Mr Inslee said. “This has happened because we have changed the climate.”
Meanwhile, in California, smoke from massive wildfires is helping crews corral the deadliest blaze of the year.
However, despite the progress there was concern that the death toll could mount as crews reach devastated areas.
Nine people, including a 16-year-old boy, have been confirmed dead since fires that started weeks ago as a result of lightning strikes fused into a monster that largely destroyed Berry Creek, a tiny hamlet in the Sierra Nevada foothills northeast of San Francisco.
Crews made progress on Friday in chopping or bulldozing brush-free lines to control the North Complex fire.
In addition, gusting winds that whipped up the flames days earlier eased while smoke blocked out the sun and lowered previously scorching temperatures.
Saturday’s high temperature was expected to top out at 27C or less.
Nearly 15,000 firefighters are battling 28 major wildfires across California, although 24 were sparked on Thursday and quickly contained.
The North Complex remains the deadliest this year, with nine confirmed deaths.
Butte County Sheriff Kory Honea had said 10 bodies were found, but on Friday that figure was lowered.
The sheriff said remains found in a burned storage shed turned out to be from a resin model of a human skeleton that was used by an anthropology student.
A search continues for 19 people who remained unaccounted for.
