Why northern and southern California face drastically different wildfire risks right now

Ari Plachta, The Sacramento Bee on Jan 8, 2025

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As fire crews battle major blazes in the Los Angeles area, Northern California remains largely free of wildfire risk thanks to a stark contrast in weather patterns.

Recent months have brought normal to above-average rainfall to much of Northern California, while Southern California has entered an exceptionally dry period. Combine that dryness with an unusually strong Santa Ana wind event, and the fires quickly erupted.

“The lack of rain and anomalous warmth and dryness that we’ve seen in the past six months, we haven’t seen it in the record going back to the 1800s,” said Daniel Swain, a climate scientist at UCLA. “Winds are the driver, but the real catalyst is this incredible antecedent dryness.”

Tens of thousands of Los Angeles area residents have been evacuated from their homes as the Palisades and Eaton fires spread rapidly across the Palisades, Malibu, Topanga, Alta Dena and Pasadena communities.

State fire authorities have reported five deaths and more than 1,100 structures destroyed by the blazes, which have burned more than 25,000 acres in two days. Those numbers are expected to rise.

Roughly two inches of rain is needed to saturate the ground and vegetation enough to significantly lower fire risk. But Los Angeles area received only a sprinkling of rain since April, leaving the region at 40% below normal precipitation, according to state data.

It’s a stark contrast to northern Sierra Nevada and foothill communities. After a reasonably active summer with the Park Fire, significant atmospheric river storms from October through December led to above average precipitation levels.

Len Nielson, Cal Fire chief for prescribed fire, said the rain has improved for prescribed burns. He is tasked with meeting the state’s annual target to light out 100,000 acres of “good fire” that can help prevent uncontrollable wildfire events by clearing excess fuel in high risk areas.

About 48,000 acres have been completed in the period that will end on June 30.

“If you look at Northern California hillsides, they’re all nice and green because we’ve gotten winter storms,” he said. “In Southern California, where it is typically dry enough for catastrophic wildfire year round, the moisture is really low.”

Climate change is also an undeniable factor at play, according to scientists. Increased heat draws moisture out of trees, shrubs — a 2016 study found that climate change enhanced vegetation drying and doubled the number of large fires between 1984 and 2015.

A 2021 study supported by the National Oceanic and Atmospheric Administration concluded that climate change has been the main driver of the increase in fire weather in the western United States.

Swain, the climate scientist, said the drastically dry air combined with strong winds are expected to continue fueling blazes. There is no rain on the forecast, he lamented.

“These fires will be burning for days, if not weeks,” he said. “The Eaton fire and the Palisades fire would be historic events individually. They will be something even greater together, and I am genuinely worried what the final toll will show in terms of human loss.”

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