Ten thousand lightning strikes in three days in the northern Bay Area of the US state of California have spread to 50,000 acres, dozens of homes have been set on fire and thousands more are feared to be on fire. A large number of residents have been instructed to evacuate.The fires hit Napa, Sonoma, and Solano counties the hardest, according to the news agency. There are about 400 places where the fire has started. Many people have been injured in the blaze.Authorities in Vicarage, a suburb of Sacramento, have ordered people to evacuate. The fire is spreading due to lightning and warming temperatures, and the use of helicopters is failing to contain the blaze.Two million people are facing power outages. A 30-year-old man has also been arrested for setting fire in the Dolan area.The fire also engulfed Colorado, covering 125,000 acres.