A series of early-season storms that drenched Californians last week lifted much of the state out of drought and significantly reduced the risk of wildfires, experts say.
It has been the wettest November on record in southern cities like Van Nuys and San Luis Obispo. Santa Barbara has received a staggering 9.5 inches of rain since Oct. 1, marking the start of the city's wettest water year on record.
Overall, the state has received 186% of its average rainfall so far this water year, according to the Department of Water Resources.
But experts say that despite the auspicious start, it's still too early to say how the rest of California's traditional rainy season will play out.
“The overall impact on our water supply is to be determined. [to be determined] is the best way to put it,” said Jeff Mount, senior fellow at the Water Policy Center at the Public Policy Institute of California. “We're not even into the rainy season yet.”
California receives most of its rain and snow between December and March, trapping runoff in its reservoirs to distribute it during the hot, dry seasons that follow.
Traffic lights along Aliso Street reflect on the Los Angeles federal courthouse on a rainy night.
(Robert Gauthier/Los Angeles Times)
Those major reservoirs are now between 100% and 145% full of average for this date. That's not just because of recent storms — early-season rains tend to soak into parched soil — but also because California is taking advantage of three previous wet winters, said state climatologist Michael Anderson.
A record wet winter of 2022-23 ended the state's driest three-year period on record. This was followed by two years that were wetter than average in northern California but drier than average in the southern half, roughly equivalent to average statewide precipitation.
According to the latest U.S. Drought Monitor report, released last week before the last of the recent storms completely swept through the state, more than 70% of California was drought-free, up from 49% the week before. Nearly 47% of Los Angeles County emerged from moderate drought, and the other parts improved to abnormally dry, the map shows. Abnormally dry conditions also ended in Ventura, Santa Barbara and San Luis Obispo counties and much of Kern County, along with parts of central California, according to the map. In the southern and southeastern corners of the state, conditions improved but still ranged from abnormally dry to moderately dry, as the map shows.
Early storms will play a big role in preparing watersheds for the rest of the winter, experts said. By soaking the soils, they will allow future storms to more easily reach reservoirs and allow snow to accumulate in the Sierra Nevada.
“Building snowpack in hydrated watersheds will help us avoid the potential loss of spring runoff on dry soils later in the season,” Anderson wrote in an email.
Snowpack is crucial to sustaining California during its hot, dry seasons because it runs into waterways as it melts, filling reservoirs and providing at least 30% of the state's water supply, said Andrew Schwartz, director of the Central Sierra Snow Lab at UC Berkeley.
The research station at Donner Pass recorded 22 inches of snow. Although that's about 89% of normal for this date, warmer temperatures mean much of it has already melted, Schwartz said. Snow water equivalent, which measures how much water the snow would produce if it melted, is now 50%, he said.
“That's really something that tells the story, so far, of this season,” he said. “We've had a lot of rain throughout the Sierra, but not as much snow as we would normally expect up to this point.”
This dynamic has become increasingly common with climate change, Schwartz said. Snow often forms later in the season and melts earlier, and more precipitation falls as rain, he said. Because reservoirs need to leave some room in the winter to mitigate flooding, they can't always capture all of this untimely runoff, he said.
And the sooner the snow melts, the more time plants and soils have to dry out in the summer heat, preparing the landscape for large wildfires, Schwartz said. Although Northern California has been spared massive fires in recent seasons, Schwartz fears his luck will run out if the region doesn't receive at least an average amount of snow this year.
For now, long-range forecasts call for equal chances of wet and dry conditions this winter, Mount said. What happens in the coming months will be key. California relies on a few strong atmospheric river storms to provide moisture; just five or seven can be responsible for more than half of the year's water supply, he said.
“We live on the edge all the time,” he said. “A handful of storms make the difference between having a dry year or a rainy year.”
Although the state's drought outlook has improved for now, scientists warn that conditions across the West are trending hotter and drier due to the burning of fossil fuels and resulting climate change. In addition to importing water from Northern California through the Sacramento-San Joaquin River Delta, Southern California relies on water from the Colorado River. That waterway remains sparse, and its largest reservoir is only one-third full.
What's more, research has shown that as the planet has warmed, the atmosphere has become thirstier, absorbing more moisture from plants and soils and ensuring dry years are drier. At the same time, there is a healthy debate about whether the same phenomenon is also making rainy periods wetter, as warmer air can retain more moisture, which could enhance storms.
As a result, swings between wet and dry from year to year, and even within a year, appear to be increasing in California and elsewhere, Mount said. That increased uncertainty has made water supply management more difficult overall, he said.
Still, because of its climate, California has plenty of experience dealing with such extremes, said Jay Lund, professor emeritus of civil and environmental engineering at UC Davis.
“We always have to be preparing for floods and for drought, no matter how wet or dry it is.”
Times staff writer Ian James contributed to this report.
