It’s been a record-setting year for wildfires in California. More than 820,000 acres across the state had burned by mid-August—more than twice the area that had burned by that point last year. In Northern California, the fire known as the Mendocino Complex last month became the largest in state history, scorching an area larger than Los Angeles. At the same time, thousands of firefighters were battling about a dozen other major blazes in California (see map), including two more that ranked among the biggest in state history. California is no stranger to wildfires, but they have gotten more destructive in recent years for a few reasons, scientists say. One is that more people have moved into remote wooded areas prone to wildfires. On top of that, global warming has intensified heat waves and droughts, which dry out trees, shrubs, and grassy areas, creating the perfect fuel for the flames. Crystal Kolden, a fire scientist at the University of Idaho, predicts these types of megafires will continue to get worse in the future. “We’re going to have more of these large fires,” she says, “more extreme fire behavior, and more intense fires.”