California has a rainy season in the winter and a no-rain season in the spring-summer-fall.
What grows naturally in most of California is low scrub bush and long grasses.In the early spring, these plants grow rapidly. There’s a sort of race among the plants to grow fastest (to soak up all of the water while there still is some). Then, the plants bloom in March/April, when we get the first few hot days (and the water is finally all gone). After that, the vegetation all dies back, leaving just the root structure alive. As the summer progresses, this becomes more and more complete. By July/August, very, very little is still green in the wilderness areas.
Then, the summer is extremely hot, with temperatures exceeding 100 F, and humidity falling sometimes as low as 6-7%. These super-hot, extra-dry days usually coincide with a local wind condition (the “Santa Ana winds” — a type of Adiabatic wind) which brings gusty winds that are erratic and sometimes blow at near-hurricane-force.
In these conditions, any ignition source is extremely likely to become a wildfire, as an ember landing anywhere will ignite some brush, and the winds will whip new embers off in an erratic path to land amongst more fuel.The result is a raging wildfire front that often moves at 20mph+, consumes most everything in its path, and periodically starts new fires up to 2 miles away as embers escape.
Additionally, much of the wildland areas are extremely rugged, mountainous terrain, which aids the fire in spreading (the winds just fly down any channels or canyons) and also severely hamper firefighters, as the fire can quickly move over an impassible-to-humans ridge, requiring lots of time for ground crews to catch up.
It’s quite hot and dry there. The climate dries out lots of the underbrush, making it easy fuel.
Areas like that are also supposed to naturally burn. Forest fires are actually quite beneficial as they clear out the underbrush, fertilize the ground, and actually cause some species of trees to start growing (the fire is a vital step in their reproduction). However, many people stop fires from happening so the dry underbrush builds up for years. When it finally does catch there’s several years worth of material there and the fires get large and out of control.
California’s natural climate for the majority of the state is semi-arid brush land. Even the forests in the north evolved to have frequent fires as many of the trees, such as the giant redwoods require fire for their seed pods to open and the seeds to sprout.
California spent decades trying to put out every small fire that ever happened and so the natural brush that would burn off every year built up. Now fires simply grow beyond what can e contained due to years of buildup.
Fire is a completely natural part of the California ecosystem. Fire damages are not…these occur when humans place buildings and infrastructure in harms way by misunderstanding the role of fire in California’s ecosystems. We attempt to control fire in locations that are close to residential developments, but that just forestalls the inevitable. When fire finally does break out in these locations, the resulting fire is more intense, rapidly moving and “ferocious” because of all the fuel that has built up. What should we do? Prohibit new development in fire-dominated ecosystems, and/or insist on fire-resistant building designs in these areas.