This story initially appeared on High Country News and is a part of the Climate Desk collaboration.
In Southern California, December wildfires are considerably unusual however not utterly out of the norm. And this yr, extraordinarily dry situations and robust Santa Ana winds created the right recipe for harmful late-year fires.
On the evening of December 9, the Franklin Fire sparked within the hills above Malibu, tearing by about 3,000 acres in simply 24 hours. As of noon December 12, the fireplace was lower than 10 p.c contained, burning simply over 4,000 acres and destroying at the very least seven buildings.
Last month, the Mountain Fire ignited beneath comparable situations in close by Ventura County, rising to 1,000 acres within the first hour. Within two days it was over 20,000 acres; 240 buildings have been destroyed earlier than firefighters contained it in early December.
And it nonetheless hasn’t rained—not for the reason that Mountain Fire, nor all through the whole fall.
It’s true that Santa Ana winds—dry winds that blow from the excessive desert out to the coast and produce low humidity, at occasions beneath 10 p.c—routinely decide up within the fall and winter. But what’s much less regular is the shortage of precipitation gripping Southern California proper now, though the area isn’t technically in a drought but.
A downtown Los Angeles climate station has recorded solely 5.7 inches of rain this yr, and never even a quarter-inch has fallen in December, which is often the center of the area’s moist season. Most years would have seen three or extra moist days by this time, sufficient to curb some wildfire danger; about 90 p.c of the area’s rainfall comes between October and the top of April.
“We are still waiting for the onset of the wet season in that part of the state, which would meaningfully wet the fuels and put the threat of large fires to bed,” mentioned John Abatzoglou, a climatology professor on the University of California, Merced.
In wetter years, the windy season presents a decrease hearth danger. But now, “when ignitions and wind collide,” as Abatzoglou put it, the panorama is primed for hearth. Dry grass and shrubs are able to burn, and the fireplace hazard forecast by the Los Angeles County Fire Department on December 11, the day the fireplace grew considerably, was excessive or very excessive all through the Los Angeles Basin, Santa Monica Mountains, and Santa Clarita Valley. “It hasn’t rained yet this season in Southern California,” mentioned Daniel Swain, a local weather scientist at UCLA. “That’s the key. That’s the real kicker.”
High winds coinciding with bone-dry vegetation is not only a downside for Southern California. Dry situations increase wildfire danger throughout the nation—through the East Coast’s spring and fall hearth seasons, for instance. And winter fires have erupted elsewhere within the West: Colorado’s fast-moving Marshall Fire sparked on December 30, 2021, morphing from a small grass hearth to a suburban conflagration—one which in the end burned over 1,000 properties—in simply an hour.