Multiple wildfires were burning across California on Monday, threatening communities and forcing people to leave their homes. The state is moving into a time of year when it usually sees its most destructive wildfires.

The Bridge Fire in the Angeles National Forest near Glendora burned at least 49,000 acres at 0% containment as of Wednesday. The fire is now the largest active fire burning in California, according to LA County Sheriff Robert Luna. It is affecting both Los Angeles County and San Bernardino County.

The 23,000-acre fire, known as the Airport fire, was one of three major wildfires in Southern California that erupted during a severe heat wave and continued to swell on Thursday. The fires have collectively displaced tens of thousands of people, charred more than 100,000 acres and strained the state’s firefighting resources.