What an onslaught of rain will mean for California’s water and wildfires

December has been a very dry month across California. But that’s about to change, with three atmospheric rivers forecast to hit the state through Christmas.

The pattern that brought an onslaught of destructive atmospheric rivers to the Pacific Northwest in recent days is now shifting south.

Rounds of heavy valley rain will hit Northern California through the weekend before moving farther south next week – bringing a risk for flooding, swollen rivers, and rock and landslides. Next week, snow will pile up across the Sierra Nevada, which have experienced significant early season snow shortfalls. Around Christmas Eve, an atmospheric river is forecast to hit Southern California.

This comes after areas from near Los Angeles to the Mojave Desert experienced a top-three wettest October to November period on record.

Although the rain will be disruptive and possibly hazardous, experts note that it’s not all bad news.

“There’s like a zero percent chance at this point, just given the antecedent rainfall, that we could see anything close to the wildfire conditions we saw last January in Southern California,” said Daniel Swain, a climate scientist with the University of California Agriculture and Natural Resources.

Stronger winds from the storms will also probably also cause an unrelenting fog bank to disperse in California’s Central Valley.

Three atmospheric rivers to hit

Concerns for flooding and dangerous travel conditions across California will be on the rise into next week with three atmospheric rivers forecast to hit the state. More than a foot of rain and 7 feet of snow could fall across parts of the northern Sierra over the next week.

Cities such as San Francisco, Sacramento and Los Angeles could receive about a month’s worth of rain or more over the next week to 10 days.

“Start to mentally prepare for a wet Christmas holiday,” wrote the National Weather Service in Los Angeles.

The first atmospheric river will hit Northern California on Friday, bringing moderate to heavy rain from Crescent City to Eureka and around Mount Shasta.

The second one, on Sunday and Monday, looks more impactful, as it could stall across Northern California, affecting areas around Santa Rosa, Mendocino, Fort Bragg and Chico.

A third atmospheric river arriving just before Christmas could be most impactful, bringing widespread heavy rain and a flood risk as well as strong winds to the state. This atmospheric river’s peak intensity is predicted to reach Category 4 out of 5 on the Center for Western Weather and Water Extremes’s scale.

But these atmospheric rivers will transport more than just moisture. They’ll also send tropical air from near Hawaii to California, where it’s been an unseasonably warm month outside of the Central Valley. It’s forecast to reach the lower 80s in Palm Springs, California, on Friday, where it’s been around 7 degrees warmer than average this month. The average high this time of the year is in the upper 60s. Dozens of high temperature records will be challenged or broken across the Southwest into next week.

Extra water

for California

The latest round of storms could make 2025 the third consecutive year with above-average precipitation across California.

Since 2013, the state has experienced four years with very low annual rainfall, each ranking in the bottom 11 % of historical observations. Over that same period, there have also been four years with very high annual rainfall, each ranking in the top 25 %.

Although California has a particularly variable climate when it comes to precipitation, Swain said these recent extremes exemplify hydroclimate whiplash, or sudden transitions from periods of flooding rainfall to drought and back again.

“I think right now in the short run, it certainly zeros out almost the wildfire hazard this season and then it also offers some more ecological recovery,” he added.

Peak atmospheric moisture flows have increased across most of California over the last three decades. For about 30 % of the state, this has contributed to frequent bouts of heavy rainfall, including most of the Sierra.

And if El Niño develops in 2026, the odds may again be shifted toward extra storms across California, as that climate pattern tends to enhance storm-steering jet stream winds.