(KGO) - Governor Brown has declared a state of emergency in Lake and Napa counties due to the effects of the explosive 50,000-acre Valley Fire burning in Lake County. Entire communities have been devastated and thousands have been forced to evacuate.

Several hundred and up to 1,000 homes have been destroyed and hundreds more are being threatened, Cal Fire says.

Cal Fire says that over 1,000 firefighters are battling this blaze but their focus is on evacuating residents.

The communities of Cobb and Middletown are burning so fast that it is challenging firefighters' ability to warn residents of the danger.

Bay Area Air Quality Management District spokesperson Aaron Richardson said there is no serious health danger from the fire, but people should take common sense precautions if they smell smoke and avoid vigorous outdoor exercise.