A wildfire in forest in north-central Arizona has grown to 17.8 square miles (46 square kilometers) but improved weather conditions could help firefighters.

Fire management team spokesman Brian Scott says higher humidity and expected cloud cover Tuesday should help nearly 600 personnel assigned to the fire in an area with numerous summer and vacation homes.

Scott says firefighters are trying to keep the fire from burning in one direction toward housing tracts and in another direction so that it doesn't enter a valley where it could burn for a long time.

Officials have estimated that the fire about 50 miles (80 kilometers) south of Flagstaff has burned 30 buildings and threatened about 1,000 homes and other buildings.

The fire is under investigation but believed to be caused by a human.