San Francisco, There have been at least 19 people killed in the past month, 3.2 million acres (about 12,950 square km) burned, and 4,000 structures destroyed in the fires across the US state of California, according to the California Department of Forestry and Fire Protection (Cal Fire).

Cal Fire Assistant Deputy Director Daniel Berlant on Sunday said that wildfires have burned more than 3.2 million acres in California, a swath larger than the state of Connecticut, Xinhua news agency reported.

About 16,570 firefighters were battling 29 major wildfires statewide Sunday. The federal, state and local resources assigned to active wildfires include more than 2,200 fire engines, 388 water tenders, 304 bulldozers and 104 aircraft, according to Cal Fire.

The August Complex in Mendocino and Humboldt counties, the largest fire in state history, grew more than 2,000 acres overnight to 877,477, and is 28 percent contained, Cal Fire officials said on Sunday.

So far, 365 structures have been destroyed and 32 damaged, and 14,074 are threatened, according to an incident report of the Creek Fire that is covering 201,908 acres with 8 percent containment.

Officials fighting the Creek Fire in Fresno and Madera counties said that forecasted wind gusts of up to 35 mph will continue to move the flames deep into canyons of the Sierra National Forest on Sunday. Their focus will be on structure defence, according to a report by the San Francisco Chronicle.

Air quality in the San Francisco Bay Area remained unhealthy on Sunday morning.