Weather provides temporary help as California's Park Fire continues to spread

Aug. 3 (UPI) -- The weather overnight helped fire crews make inroads against the Park Fire in California, state officials confirmed Saturday.

Despite the cooler temperatures and moisture, the fire remains only 27% contained and has burned through 401,199 acres across four counties over `10 days, the California Department of Forestry and Fire Protection, or Cal Fire, said in its latest update.

The latest assessment counted 567 structures destroyed and another 51 damaged to some extent.

Earlier in the week, Cal Fire declared the fire the fourth-largest in the state's history.

The blaze began July 24 and is affecting Butte, Plumas, Shasta and Tehama counties.

Thunderstorms Saturday were also expected to work in firefighters' favor, although the potential for lightning strikes increases the risk of further fires sparking the tinder-dry grass.

Shade and cloud cover produced by the smoke created moisture and moderated the fire's behavior overnight but heavy winds Saturday could also work against fire crews.

More than 6,500 personnel are currently fighting the fire, along with 45 helicopters, 536 fire engines, 153 water tenders and 194 bulldozers.

Officials have said arson is the suspected cause of the blaze after a person reportedly pushed a burning car into a gully . Police have arrested a 42-year-old man in the case.

"The fire is being carried primarily by grass and brush, mixed timber and dead and downed vegetation. The fuels are heavy, dry, and very receptive to fire. The first few days of this fire saw significant fire behavior and unprecedented fire spread," Cal Fire said in its update Saturday.

"A few days of moderated weather allowed plans to be put in place to construct containment lines. Now that hot and dry weather has returned, those lines are being tested. Spot fires and active fire behavior are expected to present challenges for fire crews the next several days."

Crews also continue to clear dried trees and brush, prioritizing populated areas.

"Fire continues to persist near communities, challenging crews in the wildland urban interface. Firefighters will continue working to open control lines from previous fires, as well as building new ones," the agency said Saturday.