Much of the northwestern United States is under a Red Flag Warning for Sunday, and also Monday for some locations. More details HERE.
The warnings will affect the three megafires in Idaho. For example on the Mustang Fire, the rather interesting forecast on Sunday is for strong winds gusting up to 29 mph. In the morning they should be out of the south in alignment with the valley along Highway 93 on the east side of the fire between North Fork and Gibbonsville, then switching to west or west-southwest in the afternoon. There will be a 13% to 28% chance of rain during the day along with a chance of lightning, but the relative humidity will bottom out at 13%.
Sunday may be a very interesting day on the fires in Idaho.