Why wildfires are so common in California

California is currently fighting through numerous wildfires. Mandatory evacuations are in effect as homes are being destroyed by the flames.

The Governor of California has declared a State of Emergency in Napa, Sonoma, Yuba, Butte, Lake, Mendocino, Nevada and Orange counties.

This news story might sound familiar to you. We see similar stories every fall as California wildfires break out. The combination of California's climatology and terrain make it a common victim of destructive forest fires.

A uniquely extreme dry season is the first reason the California is so prone to wildfires. The state receives 91% of its annual rainfall from November to April. That means by October California is 5 months into the dry season and in desperate need of rain.

Geography and terrain work to exacerbate the problem. Together they lead to the high winds that kick up during the late summer and early fall. You've probably even heard of these winds: The Santa Ana winds in Southern California and the Diablo winds in Northern California.

The weather pattern that tends to set up over California sends the winds into the states, while the valleys create tunnels to accelerate the winds. The winds push air offshore, limiting moisture from coming onshore. The winds also, of course, fan the flames of wildfires. The mountainous terrain then makes the wildfires even more difficult to control once they're burning.

While these factors make California more susceptible to fires the number one cause of forest fires is human activity. Up to 90% of forest fires across the country are traced back to human activity.