Forecasters are warning of a looming heat wave as 107 large wildfires rage in the United States, including the Dixie Fire, which has scorched 489,287 acres since mid-July, making it the second-largest single wildfire in California’s history.

The Golden State is under “widespread air quality alerts” with “scattered Red Flag Warnings” across the Northwest and Northern Rocky Mountains to parts of central California, the National Weather Service said on Sunday.