State fire Deputy Chief Gabrielle Avina said the blaze in the Pope Valley area of Napa County had burned 3,200 acres as of Wednesday morning, an additional 500 acres from the previous night.
It remained 30 percent contained. Avina said crews, however, were aided by higher humidity and lighter winds. They were expecting those conditions to hold through the day.
The fire has damaged one home and four outbuildings. In addition to the 200 mandatory evacuations, Avina says another 180 homes are threatened.
No injuries have been reported. The cause of the fire is unknown.