December fires are now a thing

This story originally appeared on High Country News and is part of the Climate desk collaboration

In Southern California, December fires are somewhat rare, but not completely out of the norm. And this year, Santa Ana’s extremely dry conditions and strong winds create the perfect recipe for dangerous year-end wildfires.

On the night of December 9, the Franklin Fire twinkled in the hills above Malibu, tear throughh about 3,000 hectares in just 24 hours. At noon on December 12, the fire was less than 10 percent contained, burning just over 4,000 hectares and destroying at least. seven structures.

Last month, the The fire of the mountain ignited in similar conditions in nearby Ventura County, growing to 1,000 hectares in the first hour. In two days it was more than 20,000 hectares; 240 structures were destroyed before firefighters contained them in early December.

And it hasn’t rained yet – not since the mountain fire, not all autumn.

It is true that the Santa Ana winds – the dry winds that blow from the high desert to the coast and bring low humidity, sometimes below 10 percent – routinely pick up in the fall and winter. But what is less normal is the lack of precipitation taken Southern California now, although the region is not technically in a drought still

A downtown Los Angeles weather station has recorded only 5.7 inches of rain this year, and not even a quarter of an inch fell in December, which is usually the middle of the region’s wet season. Most years would have seen three or more wet days at this time, enough to curtail some fire risk; about 90 percent of the region’s rainfall come over between October and the end of April.

“We are still waiting for the start of the wet season in that part of the state, which would significantly wet the fuels and put to bed the threat of large fires,” he said. John Abatzogloua professor of climatology at the University of California, Merced.

In wetter years, the windy season presents a lower fire risk. But now, “when the ignition and the wind meet”, as Abatzoglou said, the landscape is essential for the fire. Dry grass and bushes are ready to burn, and the fire hazard Forecasts from the Los Angeles County Fire Department on December 11, the day the fire grew significantly, was high or very high in the Los Angeles basin, Santa Monica Mountains and Santa Clarita Valley. “It hasn’t rained yet this season in Southern California,” he said Daniel Swaina climate scientist at UCLA. “That’s the key. That’s the real kicker.”

Strong winds that coincide with bone dry vegetation is not just a problem for Southern California. Dry conditions increase the risk of wildfires across the country – during the East CoastThe spring and fall fire seasons, for example. And winter fires are popping up elsewhere in the West: Colorado at a rapid pace Marshall Fire sparked on December 30, 2021, transforming from a small grass fire to a suburban conflagration — one that ultimately burned more than 1,000 homes — in just one hour.