Will "astonishing" ocean temperatures make California winter storms worse?
Story by Anna Skinner
• 1h
An “astonishing” Pacific marine heatwave could influence winter storms along the West Coast this year, including in California.
“If sea surface temperatures remain above normal just off the West Coast for much of the winter season, temperature departures can be even higher and precipitation much lower,” AccuWeather Lead Long-Range Meteorologist Paul Pastelok said about the forecast for the Northwest.
Why It Matters
California’s water year begins in October. The Golden State relies on heavy snow during the winter months to supplement its reservoirs. The Sierra Nevada snowpack provides around 30 percent of California’s water needs. In the spring, the snow melts and supplements local rivers and reservoirs, allowing them to carry water through the dry summer months. In 2023 and 2024, California experienced above-average snowpack due to the frequent occurrence of atmospheric rivers, which brought heavy precipitation to the mountainous regions. Last winter, California saw near-average snowpack.
However, this winter may be drier than recent years if a marine heatwave in the Pacific Ocean persists.
File photo of a snowy road in the Sierra Nevada.
What To KnowMeteorologists are beginning to issue snowfall predictions for the coming winter, but Pastelok told Newsweek there is still time for the forecast to change, particularly on the West Coast. If it continues, the marine heatwave is expected to influence winter storms.
“The waters are well-above average in many places…and that can alter upper-level patterns and storm tracks,” Pastelok said.
If California experiences a dry winter, drought could worsen, as would the likelihood of out-of-season wildfires.
Meteorologists have also addressed the heatwave.
“The North Pacific heatwave these past few months has been astonishing,” WFLA-TV Chief Meteorologist Jeff Berardelli posted on X on Sunday.
In a follow-up post, Berardelli shared a graph that showed sea surface temperatures in the North Pacific.
“Top right is how far ‘off the charts’ September 2025 sea surface temps are in this area of the North Pacific. >1.6C or ~3F above normal on average over this huge area,” he said in the post.
In late September, the California Department of Water Resources (DWR) issued an update on the state’s reservoirs as the new water year began . Lake Oroville, the state’s second-largest reservoir, is currently above average for this time of year. However, DWR officials have warned that the state “must be prepared for extreme weather events of all kinds.”
What People Are Saying
WFLA-TV Chief Meteorologist Jeff Berardelli, in a post on X about the marine heatwave: “I’d say even more alarming than the actual anomaly is the trend since 2010. In 15 years the anomaly jumped more than 2F! Much of this is likely due to the unmasking of global warming from the decrease in aerosol pollution. This allows for more ocean heating from more direct sun getting through and reduction in clouds due to feedbacks.”
California DWR Director Karla Nemeth, in a news release: “There is no such thing as a normal water year in California. Just in the past two winters, deceptively average rain and snowfall totals statewide masked the extremely dry conditions in Southern California that contributed to devastating fires as well as flood events across the state from powerful atmospheric river events. California must be ready to respond to emergencies from droughts to floods to fires.”
What Happens Next
AccuWeather meteorologists anticipate storms to bookend this coming winter, with the worst storms experienced at the beginning and end of the season. As fall gets underway, some states are already beginning to see plummeting temperatures and, in some cases, heavy snow. |
