Two major wildfires on California’s Central Coast continued to burn Monday while firefighters made progress on a third blaze in Northern California that threatened thousands of structures near Lake Oroville.

Firefighters increased containment around a fast-moving wildfire in Butte County, just south of the lake. The blaze prompted Gov. Jerry Brown to issue a state of emergency after flames destroyed more than three dozen structures and threatened 5,400 more on Sunday.

On the Central Coast, two blazes in San Luis Obispo and Santa Barbara counties have forced nearly 8,000 people to flee as flames gutted more than two dozen structures. Both fires continued to spread overnight, even as helicopters worked overtime making water drops at night, said Andrew Madsen, spokesman for the U.S. Forest Service.

After a weekend of blistering heat, firefighters will face additional weather-related complications, according to the National Weather Service .

As humidity hovers between 10% and 20%, northerly wind gusts of 40 to 45 mph will sweep across the Santa Barbara County mountains and along the southern coast, “leading to several hours of critical fire weather conditions,” the weather service said.

A firefighter maneuvers his vehicle down a private road as the Alamo fire burns near Santa Maria on July 8, 2017. The fire has charred more than 6,000 acres in remote canyons along Highway 166, fed by dry brush and trees in an area that has not burned in many years. (Luis Sinco / Los Angeles Times)

Alamo fire

The massive Alamo fire, which started Thursday off Highway 166 near Twitchell Reservoir in San Luis Obispo County, swelled more than 5,000 acres overnight, and has now burned 28,926 acres, according to the California Department of Forestry and Fire Protection.

Flames spread into northern Santa Barbara County and forced 200 people in a remote area east of Santa Maria to evacuate.

Location San Luis Obispo and San Barbara counties Acreage 28,926 Containment 20%

The blaze, which is 20% contained, is threatening 133 structures and has destroyed one home, Cal Fire said.

More than 1,600 firefighters were tackling flames burning in steep terrain loaded with chaparral and “light and flashy” grass, Cal Fire spokeswoman Toni Davis said.

A marine layer and cooler temperatures on Monday helped firefighters to dig a containment line, and Cal Fire said some flames moved further down slopes into the canyons.

Firefighters were still being challenged by steep terrain, the fire agency said.

“We are making really good progress with what we got, but we are being cognizant of what could happen,” Davis said.

The remains of a structure and boats scorched by the Whittier fire sit along State Route 154 in Los Padres National Forest near Lake Cachuma in Santa Barbara County. (Allen J. Schaben / Los Angeles Times)

Whittier fire

Burning north of Goleta, the Whittier fire, which is 25% contained, has destroyed at least 20 homes on both sides of Highway 154.

The 10,823-acre blaze started about 1:45 p.m. Saturday at Camp Whittier near Lake Cachuma in Los Padres National Forest and prompted more than 3,500 people to leave the area.

Location San Barbara County Acreage 10,823 Containment 25%

As flames broke out, the blaze trapped some 80 campers at the Circle V Ranch Camp, fire officials said. They were later rescued by a group of U.S. Forest Service firefighters.

The blaze grew more than 3,000 acres overnight and moved into the Santa Ynez Mountain ridge, said Madsen, the forest service spokesman.

Flames were smoldering in areas that have not been scorched since the 1955 Refugio fire, which burned for 10 days and charred 77,000 acres, he said.

The steep, rugged canyons are covered in decades-old chaparral, Madsen said.

On Monday, a shifting weather pattern pushed smoke over the burn area, shading the blaze and allowing firefighters to build containment lines on the fire’s edge, according to the U.S. Forest Service. By day’s end, the containment had jumped from just 5% to 25%.

Firefighters have also benefited from the higher humidity, which slowed the fire’s speed, the Forest Service said.

A plume of smoke rises as flames from the Wall fire approach Forbestown Road near Oroville, Calif., on July 8, 2017. (Josh Edelson / AFP/Getty Images)

Wall fire

More than 1,500 firefighters from across Northern California worked to contain the destructive Wall fire near Oroville on Monday.

With temperatures hovering at 88 degrees in Oroville, crews were pushing through the heat and plowing through rugged terrain to set a line around the fire, said Rich Brocchini, a Cal Fire spokesman.

Location Butte County Acreage 5,800 Containment 40%

The blaze, which is 40% contained, tore through 5,600 acres and destroyed more than three dozen structures. An additional five structures were damaged. About 4,000 people have evacuated their homes.

A combination of light grass, manzanita and oak trees has fueled the explosive fire, which started about 2:50 p.m. Friday off Chinese Wall Road, north of Bangor, Calif., Brocchini said.

Firefighters worked on four major tasks Monday – all involved keeping the fire away from Oroville, Lake Oroville and majors roads, he said.

Officials said the fire “has reduced significantly” but evacuation orders and warnings were still in place.

On Sunday night, Cal Fire said four people were injured in the fire. But on Monday, that number was revised to zero injuries, Brocchini said.

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Times staff writer Matt Hamilton contributed to this report.

veronica.rocha@latimes.com

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UPDATES:

8:45 p.m.: This article was updated with additional details on the growth of fires on Monday.

This article was originally published at 11:50 a.m.