The August 2020 California lightning wildfires (also referred to as the August lightning siege or August wildfire siege) were 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. These fires burned between to within a 2–3 week period. The August 2020 lightning fires included three enormous wildfires: the SCU Lightning Complex, the August Complex, and the LNU Lightning Complex. On September 10, 2020, the August Complex set a record for the single-largest wildfire in the modern history of California, reaching a total area burned of . On September 11, the August Complex merged with the Elkhorn Fire, another massive wildfire of , turning the August Complex into a monster wildfire of . The three major Bay Area fires, the SCU, LNU, and the CZU Lightning Complex, collectively burned about by mid-September 2020, destroyed 2,723 structures, and took 6 lives. Meteorological background Between August 14 and August 16, Northern California was subjected to record-breaking warm temperatures, due to anomalously strong high pressure over the region. Early on August 15, the National Weather Service for San Francisco issued a Fire Weather Watch highlighting the risk of wildfire starts due to the combination of lightning risk due to moist, unstable air aloft, dry fuels, and hot temperatures near the surface. Later that day, the Fire Weather Watch was upgraded to a Red Flag Warning, noting the risk of abundant lightning already apparent as the storms moved toward the region from the south. The source of this plume of moist, unstable air was the weakening Tropical Storm Fausto. Due to abnormal winds, this plume was streaming from up to off the coast of the Baja Peninsula into Northern California. This moisture then interacted with a high-pressure ridge situated over Nevada that was bringing a long-track heat wave to much of California and the West. These colliding weather systems then created excessive atmospheric instability that generated massive thunderstorms throughout much of Northern and Central California. Such thunderstorms are rare for California, but were more typical of Midwest garden-variety storms, with one location near Travis Air Force Base going from around to in nearly 1–2 hours. Additionally,