For anyone heading to California’s coast this season, the ocean is not behaving the way it usually does.
From San Diego to Los Angeles and up toward the Bay Area, coastal waters have stayed unusually warm for months, with some locations setting record high temperatures. At the Scripps Pier, ocean temperatures have reached record levels on more than 30 days this year.
Scientists call it a marine heat wave — a prolonged period of ocean temperatures well above normal that can reshape marine ecosystems and change what people experience at the beach.
And this year, the impacts are showing up along the shoreline in ways beachgoers can see, smell, and sometimes avoid.
What is a marine heat wave?
A marine heat wave is a period of unusually warm ocean temperatures that lasts for days, weeks, or even months, according to the National Oceanic and Atmospheric Administration. It happens when water temperatures rise well above normal for a given time of year and location.
These events can be driven by a mix of factors, including changes in ocean currents, persistent weather patterns, and larger climate systems such as El Niño. While warm spells in the ocean can happen naturally, scientists have found that marine heat waves are becoming more frequent, more intense, and longer-lasting in many parts of the world.
Along the California coast, these warm periods can affect everything from fish movement and marine ecosystems to beach conditions and coastal weather patterns.
How will this impact California beaches
Warmer ocean water does not stay offshore — it shows up along California’s shoreline in ways beachgoers can see and sometimes feel immediately. That can include:
Beach conditions can shift as well. Warmer surface waters can affect water clarity and, at times, contribute to choppier or less predictable surf.
But the impacts extend beyond the shoreline.
As ocean temperatures rise, fish species may move deeper or farther offshore in search of cooler water. Shellfish harvesting can also be disrupted during toxic algal blooms associated with warm conditions. In some cases, these changes lead to temporary fishing restrictions or closures as managers respond to health risks.
Those disruptions can ripple through the state’s food system, affecting seafood availability and pricing across California — including inland restaurants, grocery stores, and markets that rely on coastal fisheries.
How it can affect coastal weather in California
The ocean plays a central role in regulating California’s climate. When sea surface temperatures run hotter than normal, that balance shifts.
Along the coast, that can translate into more humid air, warmer overnight temperatures near the shoreline, and a reduced version of the typical coastal cooling effect many Californians expect during beach trips.
While not every marine heat wave leads to extreme or disruptive weather, sustained ocean warmth can increase the likelihood of unusual or less predictable coastal conditions, especially during extended warm periods.
Why is this happening
Marine heat waves are not new, but scientists say they are becoming more common and lasting longer.
A combination of natural climate variability and long-term ocean warming trends drives them. Events such as El Niño can intensify warm conditions in the Pacific, but the broader background warming of the ocean is raising baseline temperatures across the region.
When ocean temperatures remain elevated for extended periods, the effects do not stay offshore. They ripple through marine ecosystems, fisheries, and coastal conditions, influencing everything from fish distribution to water quality along the shoreline.
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Brandi D. Addison covers weather across the United States as the Weather Connect Reporter for the USA TODAY Network. She can be reached at baddison@gannett.com. Find her on Facebook here.
This article originally appeared on Palm Springs Desert Sun: Going to the beach? What California’s marine heat wave is changing
Reporting by Brandi D. Addison, USA TODAY NETWORK / Palm Springs Desert Sun
USA TODAY Network via Reuters Connect
