FILE — Firefighters battle a large brush fire on Friday, Aug. 10, 2018, near White Swan, Wash. 

The National Weather Service has issued a red flag warning for high fire danger affecting much of Eastern Washington.

The warning goes into effect at 2 p.m. Thursday and includes most of the state east of the Cascades. It's scheduled to run until 9 p.m.

Meteorologists forecast sustained winds of 10 to 20 mph with gusts as strong as 40 mph combined with relative humidity below 25% — ideal weather for fire to spread. They're warning of the potential for extreme fire behavior during the warning period and advise everyone to avoid outdoor burning.