A new assessment of the Sunnyside Turnoff Fire burning outside the town of Warm Springs shows that flames have scorched more than 45,000 acres. That's more than double previous estimates.
Fire managers say the fire is still growing, but the increase is largely the result of more accurate mapping. Officials are reporting 40 percent containment.
Meanwhile, the National Weather Service has issued Red Flag Warnings for much of Central Oregon.
That has firefighters like Ben Duda on alert for new starts. Duda directs engine crews for the the Oregon Department of Forestry out of Sisters.
He says said warnings indicate atmospheric instability, and that tends to produce taller clouds that can give off lightning.
"It also can affect existing fires that are on the ground right now," Duda said. "So, literally, like, you've got a fire going in the stove already and you open the flu up more and it just starts cranking and really increases the fire intensity."
The extreme fire potential has officials reminding the public to exercise caution and follow local fire restrictions. Forecasters are predicting scattered lightning could persist in Central and Eastern Oregon into Friday.
This story originally appeared on Oregon Public Broadcasting.