For much of the western U.S., record summer heat is expected to bleed into the fall, as California keeps working to contain some of the largest and most destructive wildfires the state has ever recorded. After an abnormally dry winter and sustained heat since then, land managers were already anticipating an active fire season. However, the size and intensity of this year’s fires has prompted discussion of a new “megafire era,” as climate change continues to add to the already heaping tinderbox of wildfire risk.

The West has warmed nearly two degrees on average since the 1980s, while the number of acres burned by wildfires has exploded. In California, over 12 million acres have burned between 1980 and 2019, which is more than any other western state included in our analysis. This year’s fire season in California has already surpassed its all-time record of acres burned, which was set in 2018. Higher temperatures mean more evaporation, which worsens drought and dries out vegetation, elevating the risk of a fire igniting and spreading. One study found that climate change has resulted in a doubling of forest fire acres between 1984 and 2015.

Human development has increasingly encroached on forested areas, suppressing natural fire regimes and exposing more communities to the risk of wildfires. The increasing size of wildfires coupled with more people and homes at risk also puts a strain on emergency services. Even hundreds of miles from a blaze, smoke waves from wildfires can endanger public health 一 particularly among at-risk populations, including people with chronic health conditions and outdoor laborers like farm workers.