OKANOGAN - The Spokane office of the National Weather Service has issued a red flag warning calling for low humidity and gusty winds.
In a statement, officials said temperatures will be in the mid to upper 90s and relative humidity will be near 10 percent.
"Gusty north winds of 10 to 20 mph are forecast for Friday which will likely create critical fire weather conditions down the Okanogan Valley," officials said.
The warning will remain in effect until 9 p.m. tonight, at which time officials could call it off or extend it.
"Rapid fire spread is likely with any new or existing wildfire in the Okanogan Valley on Friday ," officials said.
A red flag warning means that critical fire weather conditions are either occurring now, or will shortly. A combination of fierce winds, low relative humidity and warm temperatures can contribute to extreme fire behavior, officials said.
Along with the warning, most of eastern Washington remains under an air quality alert.
"Smoke from wildfires in eastern Washington, British Columbia and Montana is expected to affect central and Eastern Washington as north or northeast winds push smoke around Washington state this week," officials said. "Air quality will vary between good an unhealthy depending on wind direction and time of day."
Officials said children, senior citizens and people with respiratory illnesses are most at risk of serious health effects.
Okanogan County Public Health in conjunction with Okanogan Emergency Management has established distribution places in Okanogan County for N-95 masks.