TWIN wildfires are threatening 10,000 homes in Northern California in a seemingly endless summer of blazes that have ravaged some of the most scenic areas of the state.

The two fires straddling Mendocino and Lake counties had burned seven homes by Monday night along with 107 square miles of rural land.

About 100 miles north, the so-called Carr Fire which has burned more than 800 homes and killed six people has become the ninth most destructive wildfire in Californian history, said Scott McLean, a spokesman for the California Department of Forestry and Fire Protection.

In Lake County, evacuation orders were in effect for the 4700 residents of Lakeport, along with some smaller communities and a section of Mendocino National Forest. In all, 10,000 people have been warned to flee.

Aircraft made continuous water and fire retardant drops on the blaze.

Further north, police said five people were arrested on suspicion of entering areas evacuated due to the wildfire around Redding.