Los Angeles, California - Firefighters were battling a fast-moving wildfire in California on Thursday, authorities said, with more than 3,500 people forced to flee their homes.

The Park Fire, enveloping more than 71,000 acres, broke out Wednesday evening, on the last day of a heat wave affecting the region.

More than 1,150 personnel were deployed to fight the blaze, which was only three percent contained, according to the California Department of Forestry and Fire Protection (CalFire).

As of 12:00 PM local time on Thursday, the fire had enveloped 71,489 acres, according to CalFire.

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More than 3,500 people had evacuated the area, Governor Gavin Newsom said.

The town of Chico, under threat from the fire, is located just 12 miles west of Paradise, a town that was destroyed by a massive wildfire in 2018, resulting in the deaths of 85 people.

The cause of the Park Fire remains under investigation, according to CalFire.

On Thursday, the National Weather Service issued a "red flag" weather warning for "critical fire weather conditions" in the area, including wind gusts and low humidity.

The western US has experienced several heat waves since the beginning of June, and dozens of fires are currently burning in the region.

Oregon, California's northern neighbor, is battling a megafire that is the largest in the country, having ravaged more than 268,000 acres of forest and prompting evacuations in a rural region.

The raging flames have created vast columns of smoke, affecting air quality as far away as neighboring Idaho.

Wildfires were also burning in western Canada, where part of the tourist town of Jasper has been destroyed.

Western North America has increasingly been affected by extreme weather events, exacerbated by climate change.

In mid-July, Newsom warned of a fire season that was "shaping up to be very active."