The August 2020 California lightning wildfires (also referred to as the August lightning siege or August wildfire siege) are a series of 650 wildfires that ignited across Northern California in mid-August 2020, due to a siege of dry lightning from rare, massive summer thunderstorms, which were caused by an unusual combination of very hot, dry air at the surface, dry fuels, and advection of moisture from the remains of Tropical Storm Fausto northward into the Bay Area.[4][5] These fires burned between 1,500,000 acres (6,100 km2) to 2,100,000 acres (8,500 km2) within a 2–3 week period.