Three massive wildfires raging near the San Francisco Bay Area, which started a month ago due to lightning strikes, were almost completely contained, according to the California Department of Forestry and Fire Protection (Cal Fire).

The LNU Complex Fire in the North Bay, the SCU Complex Fire in the East Bay, and the CZU Complex in the San Mateo and Santa Cruz counties were all 98 per cent contained on Saturday morning, Xinhua news agency quoted Cal Fire as saying in its latest update.

The state's biggest-ever fire, the August Complex in Mendocino and Humboldt counties that has raged through 832,891 acres, was 30 per cent contained by Saturday morning.

The fire burned mainly through forest land, destroying 51 structures and causing thousands of evacuations.

More than 2,100 firefighters, including out-of-state aids from Montana, New Jersey, Texas and Idaho, are battling the blaze, according to a report by the San Francisco Chronicle.

Meanwhile, the North Complex Fire, raging in Butte, Plumas and Yuba counties, has killed 15 people and damaged 1,147 residential and business buildings.

It became the fifth-largest fire in California's history on September 17 and burned 289,951 acres with 58 per cent containment as of Saturday.

Nearly 3.5 million acres of land have burned from wildfires in California so far this year, 26 people have died and nearly 6,300 structures have been destroyed, according to Cal Fire.

The Bay Area was expected to enjoy clean air and clear skies this weekend and into next week, according to the National Weather Service.

But no rain is expected for the next 10 days to two weeks.

According to Cal Fire, five of the top 20 largest fires in California's history have occurred in 2020.

California's peak fire season usually runs until October, but can continue until further in the year..