Thousands of people across California remained under evacuation advisories Monday as authorities battled wildfires that erupted over the weekend and torched thousands of acres while weather officials warned of more strong winds and dry conditions.

The so-called Post Fire broke out Saturday afternoon and, fueled by powerful wind gusts, has burned 14,625 acres of dry, mountainous land about 60 miles northwest of Los Angeles, according to the California Department of Forestry and Fire Protection. Through the weekend, as the blaze expanded south along Interstate 5, it triggered mandatory evacuation orders and other warnings.

More than 1,200 people fled from Hungry Valley Park, a popular destination for off-roaders and bikers known for its scenic motorcycle trails. To the south, authorities closed Pyramid Lake, a reservoir popular for weekend boating about 25 miles northwest of the city of Santa Clarita. A several-mile stretch south of Pyramid Lake was placed under an evacuation warning.

Firefighters battled the blaze as it approached Lake Pyramid overnight but were hampered by limited visibility as they tried to establish a perimeter on the fire's east side, Cal Fire said. One commercial structure has been destroyed by the flames. The cause of the fire was unknown.

The National Weather Service issued a red flag warning for the I-5 corridor in northwest Los Angeles County, warning of high temperatures, low humidity and wind gusts of 30 to 50 mph through Monday afternoon. Tuesday also could see strong northerly winds.

"These conditions will be favorable for the rapid growth and spread of wildfires, including the ongoing Post Fire complex," the weather service said.

Mika Olesen, 20, who lives in Castaic, a suburban outpost northwest of Santa Clarita, said smoke and embers have blown into town since Saturday evening as the blaze moves south.

"It's hazy over the the mountains," said Olesen, who has never had to evacuate because of a wildfire and hoped the blaze would be extinguished before it reaches more populated areas, like Castaic.

Blaze near Lake Sonoma prompts evacuation orders

In Northern California, firefighters battled another fire that has engulfed more than 1,000 acres across Sonoma County.

The fire began just east of Lake Sonoma, about 25 miles northwest of Santa Rosa, and within hours authorities ordered evacuations for hundreds of residents between the lake and the small city of Healdsburg. Thousands have been placed under evacuation warnings.

At least one firefighter has been injured in the blaze, which has been dubbed the Point Fire, according to Cal Fire. About 400 first responders have been sent to the scene, and authorities used helicopters, bulldozers, water tenders and 50 fire engines to battle the blaze.

Multiple structures were damaged and destroyed, through the exact number of buildings remains unclear. Through the night, firefighters used three helicopters in their latest attempt to quell the flames amid strong winds and low relative humidity, Cal Fire said. As of Monday, the blaze was 20% contained.

Authorities said the cause of the fire was under investigation.

Nearby areas, including North Bay and Contra Costa counties, issued Spare the Air advisories, warning that the air may be unhealthy for sensitive groups. Authorities temporarily banned wood burning and urged residents to avoid smoke exposure.

"Protect your health, stay indoors," the advisory says.