The massive and deadly wildfires that swept through California's wine country this week were helped along by near perfect conditions for explosive fire growth, allowing the fires to start and spread very rapidly.
For starters, California is coming out of over 5 years worth of extreme drought, providing a ton of very dry heavy fuel in diseased and dry trees and brush. Record rainfall that started to break the drought produced a bumper crop of fine fuels, like grasses, to act as tinder and kindling for the heavier dry brush. This combination provided way too much fuel for the fires to consume once they started.
The next ingredients came in the form of very dry air (low relative humidity) and high winds. At times, wind gusts were at or over 70 mph. The stronger the wind, the faster and more widely the fire can spread once it gets started. The very strong winds in California got the fires to accelerate very rapidly once they started.
According to NBC News, authorities grappled with containing the 22 firestorms raging simultaneously across the state's wine country, including Napa and Sonoma counties.
Ken Pimlott, director of the California Department of Forestry and Fire Protection, or Cal Fire, said at least 115,000 acres had burned so far — about 2½ times the size of Washington, D.C. Firefighters from across California and Nevada were called in as reinforcements.
Napa County Fire Chief Barry Biermann said at a news conference: "The fires are still out there, and they are still actively growing."
While the loss of life and property is devastating, there is a silver lining to wildfires like these: they can lead to healthier grasslands and forests, and help cut down on further extreme wildfires. The fires can remove dead and diseased trees and plants, and kill off diseases and insects that cause dead, dry trees in the first place, eliminating future fuels for fires. The fires also clean up the forest floor, leading to healthier trees. Fires can also remove heavy brush, providing better habitats for wildlife and other plants in the future.