Smoke and ash have been raining down near Lake Berryessa in the US state of California where wildfires have been spreading. <br /><br /> Fire extinguishing planes, helicopters, and more than 700 firefighters have been battling a major blaze just north of San Francisco’s Bay Area that’s scorched 4,000 acres of grass and woodland since it erupted on Tuesday.<br /><br /> Officials have urged people to stay indoors because of thick smoke.<br /><br /> A long drought and extreme summer heat across the region have hampered efforts to quell the blaze. <br /><br /> The so-called Cold Fire is one of 30 major wildfires reported to have scorched about 700 square miles mostly in the west of the US.<br />
