"The fire will continue to be extremely active with gusty winds and extremely dry fuels," says an update posted to InciWeb, the national clearinghouse for wildfire information.
Officials in recent days have touted progress against the massive fire, which was started July 6 by lightning.
"Fire crews and support personnel have made significant progress in containing this fire in the last few days," Joe Prummer of the Northwest Interagency Incident Management Team said. "However, we still have a long road ahead of us to ensure the safety of the surrounding communities."
The blaze grew about 4,000 acres Thursday and officials said there was growth and activity in two areas but the advance was controlled with bulldozers.
It is now the third-largest fire in Oregon since 1900, Marcus Kauffman, spokesperson for Oregon Department of Forestry, told CNN's Poppy Harlow on Thursday.
More than 2,100 people under some form of evacuation due to the fire, according to Kauffman.
Record-breaking, triple-digit temperatures and severe drought have devastated parts of Oregon. Those conditions have been fueling the fire and forcing evacuations.
Doug Grafe, chief of fire protection at the Oregon Department of Forestry, this week predicted a "long, difficult fire season."
He said Tuesday -- when the fire had burned 388,000 acres -- it's possible that another 50,000 to 100,000 acres could burn before the Bootleg Fire is contained.
"The future for us for the remainder of the season continues to look above normal dry and above normal temperatures," Grafe said. "So this is not going to return to normal anytime soon."
A ban on campfires will be banned in state parks and state-managed forests east of Interstate 5 started Thursday, the Oregon Parks and Recreation Department said. That covers all regions of the state except the Pacific coast and a portion of the Willamette Valley.
The ban includes not only charcoal and propane fires, but also tiki torches and even candles.
People in other areas of US getting short break from thick smoke
But by Thursday night, smoke from wildfires could return, before another front will push through the region on Saturday into Sunday to help clean it out again, according to CNN meteorologist Michael Guy.
This will be the pattern until the jet stream changes direction and/or the fires have diminished, he said.
The intensity of the fires was so strong that high-level winds had carried their smoke to the East Coast, where New York City recorded its worst air quality day in over a decade.
The city saw a 24-hour average Air Quality Index of 154 on Tuesday, the worst it's been since June 2006, when the AQI was 157.
And in Canada, a state of emergency was declared for British Columbia, where 3,180 firefighters are working on 300 fires across the province, officials said.
More fires ravage US lands
The NIFC says eight active large fires in California have already burned more than 230,000 acres and additional evacuations were issued Wednesday around the Dixie Fire in Butte and Plumas counties.
Following Oregon, the states with the most acres burned are California, Idaho and then Alaska.
On Tuesday, Pacific Gas and Electric said the fire may have been sparked by equipment it manages.
In a preliminary filing with the California Public Utilities Commission, PG&E detailed an outage alert July 13, the same day the fire started. A responding utility worker found three blown fuses and a tree leaning into a pole, with a small fire on the ground near the base of the tree.