Southern California’s winter 2025-2026 has been shaped by La Niña conditions, which historically push the region toward drier-than-average outcomes. La Niña has been active since fall 2025, with sea surface temperatures in the east-central Pacific running about 0.9°C below normal as of January 2026. That pattern typically steers storms away from the southern half of California, though the full picture is more complicated than any single climate signal suggests.
How La Niña Steers Storms Away
La Niña’s influence on Southern California comes down to the jet stream, a river of fast-moving air high in the atmosphere that guides storm systems across the Pacific. During La Niña, the Pacific jet stream shifts northward, meandering up toward Alaska and the Pacific Northwest. That rerouting pulls the storm track well above Southern California, leaving the region warmer and drier than normal while delivering extra rain and snow to Washington, Oregon, and Northern California.
This isn’t a subtle effect. NOAA describes it as a defining feature of La Niña winters: the entire southern tier of the United States, from California to the Carolinas, tends to run dry. For Southern California specifically, that means fewer of the large Pacific storms that deliver the bulk of the region’s annual rainfall.
Atmospheric Rivers: The Wildcard
La Niña sets the odds, but atmospheric rivers can override them entirely. These narrow corridors of moisture-laden air stretching across the Pacific deliver roughly 40% of Southern California’s annual precipitation. Just one or two powerful atmospheric rivers landing in the right spot can flip a dry year into a wet one, regardless of what the broader climate pattern predicts.
Research from the Scripps Institution of Oceanography found that about 32% of years studied went against expected patterns from El Niño and La Niña. Atmospheric river activity explained roughly 70% of those surprises. The 2023 La Niña year is a striking example: nine atmospheric rivers hit California in sequence, producing the state’s 10th wettest year on record despite La Niña conditions that should have kept things dry. Similar reversals happened during La Niña years in 1967, 2011, and 2017.
As one Scripps researcher put it, atmospheric rivers are “the precipitation wildcards in the Western U.S.” Their timing and intensity are difficult to predict more than a week or two in advance, which means seasonal forecasts based on La Niña alone carry real uncertainty.
What the Data Shows So Far
California’s reservoirs tell a useful story about how the current water year is playing out. As of early March 2026, statewide reservoir storage sits at about 30.9 million acre-feet, roughly 125% of the historical average. That’s a strong position, suggesting that even if the rest of the season runs dry, California entered this winter with a solid water buffer built up from previous years.
La Niña itself is fading. NOAA projects a 60% chance of transitioning to neutral conditions between February and April 2026, with neutral conditions likely persisting through summer. That weakening means the jet stream pattern pushing storms northward may loosen its grip as the season progresses, potentially allowing late-season storms to reach farther south.
Fewer Storms, but Potentially Intense Ones
Even in a drier-than-average winter, the storms that do reach Southern California can be severe. California’s Department of Water Resources has flagged a growing pattern: as the climate warms, precipitation increasingly arrives in concentrated, intense bursts rather than spread across many moderate storms. That means a La Niña winter with below-average total rainfall can still produce dangerous flooding events when individual storms hit hard.
This is especially relevant for Southern California, where steep terrain, fire-scarred hillsides, and urban development amplify flood risk from heavy rain. A single atmospheric river parked over the region for 24 to 48 hours can deliver a month’s worth of rain, triggering mudslides and flash flooding even in a year that registers as “dry” in the final tally.
The Bottom Line for This Winter
The odds have favored a drier-than-average winter for Southern California in 2025-2026, consistent with what La Niña typically delivers. But “drier than average” doesn’t mean no rain, and the atmospheric river wildcard means surprises are always possible. Roughly one in three La Niña years breaks the expected pattern, often because of a few well-timed moisture plumes from the Pacific. With La Niña weakening and a transition to neutral conditions expected by spring, the strongest dry signal may already be fading. Reservoir levels remain healthy at 125% of average, so even a below-normal year doesn’t put the state in an immediate water crisis.