Two highways in Okanogan County remained closed Friday morning, officials said. At least two houses had been damaged by mud.
Some drivers were stranded by mudslides, but no injuries were reported.
The thunderstorms that hit the area in north-central Washington brought flash flooding Thursday that affected the fire teams.
"Flash flooding has impacted our fire operations and incident command post," the fire management team said on Facebook late Thursday. "We are ensuring all resources are accounted for, and that everyone has a dry place to sleep."
The Carlton Complex fire, which began July 14 as four separate fires in the Methow Valley, grew quickly into the largest fire in the history of Washington. It has burned more than 400 square miles in Okanogan County.
The fire and others in the area stripped hillsides of vegetation, leaving them vulnerable to slides and flooding.