Photos: The Line wildfire in Southern California burns over 20,000 acres and forces thousands of evacuations

The "Line Fire," a fast-moving wildfire fueled by extremely high temperatures in San Bernardino County, Calif., has scorched more than 20,000 acres of land and forced thousands of Southern California residents to evacuate over the weekend.

As of Monday morning, the wildfire — which first broke out on Thursday evening — is 3% contained as more than 600 firefighters battle to contain the flames. California firefighters also warned that areas of smoke "could become more widespread in the afternoon."

California Gov. Gavin Newsom declared a state of emergency Saturday night in San Bernardino County, which is located a little over 60 miles east of Los Angeles. The declaration allowed the state to secure additional federal fire management assistance.

"I thank President Biden for his swift approval of support for the work of our firefighters and first responders battling this fire and protecting local communities," Newsom said in a statement. "It's critical that residents in the impacted areas remain vigilant and prepare to evacuate immediately if called for by local authorities."

More than 36,000 structures are being threatened, California firefighters reported Monday, including homes and businesses in the wildfire’s path.

The Line Fire has been fueled by a late-summer heat wave. An excessive heat warning is in place until Monday night as meteorologists predict temperatures to climb up to 108 degrees as the fire spreads in the northeast direction.

The cause of the wildfire is under investigation.

See more of our photo features on Yahoo News >>>