A sunset crests over the Scripps Pier in La Jolla.
Erik Jepsen
Hottest. Earliest. Most extreme. California’s meteorologists and oceanographers keep dropping new superlatives about the temperatures in 2026.
In the first months of the year, a record-smashing heat wave set a new high for the hottest California day in March and prompted a premature spring. Now, experts are turning focus to the heat simmering deep in the Pacific Ocean, which is already likely hurting marine life.
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“There’s a bunch of claims circulating, some viral social media posts, that this is the most extreme heat wave, oceanic heat wave ever observed in this region, so is that true?” Daniel Swain, a climate scientist for the University of California’s Agriculture and Natural Resources, said during a recent videostream. “Well, by many objective metrics, yes, that is correct.”
The Pacific Ocean is baking for thousands of miles, from about San Francisco all the way to Guatemala, according to recent sea surface temperature data from the National Oceanic and Atmospheric Administration. In this data set, a massive splotch of dark maroon concentrated from California’s Central Coast into Mexico — and also far west offshore — depicts many spots with temperatures ranking in the highest percentiles.
“The 100th percentile here would mean, for example, the single warmest value ever observed,” Swain explained, “and the 98 percentile means that only 2% of all historical observations were warmer.”
Smack in the middle of this unprecedented marine heat, scientists from the Scripps Institute of Oceanography at UC San Diego maintain one of the most robust data sets for the sea. They monitor daily temperatures at 10 coastal stations across California, including ones at the Scripps Pier, Newport Beach, Pacific Grove and the Farallon Islands with more than 100 years of data.
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Since November 2025, many of these stations have broken daily, all-time record highs for water temperature, according to Scripps. Most readings have ranged upwards of 2 to 4 degrees Fahrenheit warmer than the high historical temperatures for the time of year, a significant rise for ocean waters. Since Jan. 1, at least 36 days of temperature readings off the Scripps Pier broke daily records.
The red dots indicate the daily records broken at Scripps Pier in 2026.
Scripps Pier, La Jolla, Shore Stations
Beyond the surface, there’s evidence the warm layer extends far offshore and deep down as well, according to the Scripps scientists who send robotic underwater gliders out to sea for months of exploration.
Deadly heat for marine life
The deep-sea temperature rise is just shy of that during the infamous “blob” of warm water from roughly 2014 to 2015, which led to a cascade of impacts on marine life. Species like hammerhead sharks, bluefin tuna and red crabs traveled north; baitfish like anchovies thrived while sardines did not, affecting commercial fisheries; seabirds, seals and sea lions starved; kelp suffered; harmful algal blooms took off.
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The current heat wave is likely fueling the seabird die-offs in Central and Southern California in recent months. Researchers in San Diego conducting monthly beach surveys for dead seabirds and marine mammals have found a spike in the numbers of dead brown pelicans, Brandt’s cormorants and common murres.
“If the ocean is warmer than normal, it can impact the food web in multiple ways,” Tammy Russell, a marine seabird expert at Scripps, said in a statement. “Fish and other organisms that require cooler waters to survive can move to cooler locations (north or deeper), resulting in lower food availability in warmer regions. Additionally, warmer conditions can stratify the water column, reducing the nutrient supply that reaches the surface waters and have cascading impacts on the entire food web.”
Since most of the birds look emaciated and test negative for HPAI, or avian flu, the scientists have concluded that starvation is driving the mortality event.
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“I think it’s fair to say there are winners and losers in marine life, and a lot of that depends on whether an organism can move or not,” Dan Rudnick, a physical oceanographer for Scripps, told SFGATE. “When we have warmer water, we’ll see more species that prefer warmer water here, more tropical species off Southern California. On the other hand, some organisms that can’t move will be worse off because they’re adapted to colder temperatures. If it stays warm for a very long time, we can have kelp die-offs, for example.”
Jamin Greenbaum’s RIFT-OX floating platform being tested off Scripps Pier in December 2025.
Erik Jepsen/UC San Diego
Interactions with El Niño
El Niño conditions, expected to develop later this year, could amplify the marine heat wave. El Niño is the warm phase of a pattern that emerges in the tropical Pacific Ocean, called the El Niño-Southern Oscillation, or ENSO. During El Niño events, weak trade winds are associated with above-average surface temperatures in those waters.
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In the past, warmer waters off California originated with El Niño, but this current heat wave formed for different reasons. For Rudnick, weaker winds, slowing down the upwelling of deep-sea cold waters, was one possibility, but he said he was still studying some additional explanations.
“So far, this has not actually related to El Niño,” Swain agreed. “This is something else. But the developing El Niño event might actually amplify it, causing this marine heat wave to last longer and become even stronger than it otherwise might have been.”
El Niño patterns tip the odds in favor of a wetter winter, especially in Southern California, but it’s not completely predictable. The marine heat wave alone is expected to impact the weather in myriad ways, such as bringing humidity, driving away fog and even affecting Pacific hurricane season.
And how long will it last? A heat wave in the air can snap back to cooler temperatures in just a few hours, but when a vast volume of water is involved, ocean heat grows and dissipates more slowly.
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“When there’s this much warm water, it’s just not going to disappear overnight,” Rudnick, who runs the glider program for Scripps, said. “Heck no. It took months to get this way, and it’s going to take months to go away, too.”
Swain emphasized that this all folds into a bigger narrative about climate change. Sometimes natural cycles can compound human-caused warming and other times they counteract it, he explained. In recent years, the coast has been cooler than average, soothing the warming ocean.
“The oceans are getting warmer because of human-caused warming and accumulation of heat-trapping gasses in the atmosphere,” Swain said. He added: “Natural cycles, natural variability, is now going to be in alignment, at least this summer, with the long-term warming trend. And boy howdy, does it look like it’s going to be a persistent and extreme marine heat wave.”
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