A wildfire ignited by lightning in rural northern San Diego County is now estimated to have burned 668 hectares. 

California Department of Forestry and Fire Protection spokeswoman Roxanne Provaznik says the blaze is 10 per cent contained Friday afternoon and there are thunderstorms and light precipitation in the area. 

Temperatures are hovering around 40 degrees and winds are blowing at 12 km/h with gusts to 27 km/h. 

The fire is burning in highlands northeast of the community of Warner Springs, about 80 kilometers northeast of downtown San Diego. 

Residents of the Chihuahua Valley Road area were advised to evacuate but so far no buildings have burned.