COLSTRIP, Mont. (AP) — Firefighters in eastern Montana prepared for a tough day Sunday as they faced predicted temperatures of 100 degrees, low humidity and strong winds with the possibility of afternoon thunderstorms that could spark additional blazes.

Ash Creek Complex fires spokesman Pat McKelvey says firefighters worked overnight strengthening fire lines on the 246-square-mile complex burning about 10 miles west of Lame Deer in timber, sage and grass.

He says a red flag warning stretching from the Continental Divide to the Dakotas will make Sunday a testing day for firefighters.

More than 500 firefighters are now at the complex of lightning-caused fires that started Monday and have destroyed more than 30 structures. No injuries have been reported.

Meanwhile, firefighters had the 34-square-mile Dahl fire in Musselshell County 65 percent contained Sunday.