Global ocean heat breaks record months after its usual peak

The world's oceans have reached their highest average surface temperature on record, months after temperatures typically reach their annual peak, as a strengthening El Niño adds heat to already unusually warm waters.

The average sea surface temperature across the extra-polar oceans reached 21.1 C, or about 70 F, on Aug. 22, according to the Copernicus Climate Change Service . That narrowly surpassed the previous record of 21.09 C set in March 2024.

The Copernicus analysis covers ocean waters between 60 degrees north and 60 degrees south, excluding polar regions. Its dataset extends back to 1979, when satellite observations became more reliable.

AccuWeather Lead Hurricane Expert Alex DaSilva said El Niño was in place during the fall of 2023, contributing to the warm oceans in 2023 and 2024.

The timing of the record is especially unusual. Global ocean temperatures generally reach their highest point in March or April, following summer in the Southern Hemisphere.

"Typically, March and August are when the world's oceans are at their warmest. As a result, while the waters could continue to warm for the next week or so, it is unlikely that records will continue to be set through September. Depending on how strong El Niño gets this fall, we could break the world sea surface temperature again next March when temperatures rise again," DaSilva said. "This is when 2024 broke the record. It was in March at the end of an El Niño." European Union's Space program Climate Strategic Lead Samantha Burgess said the number of marine heat wave days globally has more than tripled since the early 1990s, putting a strain on marine ecosystems and coastal communities. "This record is another clear signal of an ocean under growing stress. El Niño is adding heat to the system, but it is doing so on top of decades of human-driven warming. As ocean temperatures continue to rise, the risks to marine ecosystems and coastal communities also increase," Burgess said.

El Niño could reshape North America's weather

El Niño occurs when water in the central and eastern tropical Pacific becomes warmer than historical averages, triggering changes in the atmosphere that can shift weather patterns around the world.

El Niño is strengthening, and AccuWeather experts are highly confident the 2026 El Niño could become the strongest in a lifetime.

"For people across North America, the ocean temperature record itself is only part of the story," AccuWeather Lead Long-Range Forecaster Paul Pastelok said. "What we're watching closely is how all of this ocean warmth interacts with a strengthening El Niño. That combination can have important implications for the intensity of storms, storm tracks, temperatures and precipitation patterns across the continent in the months ahead."

Warmer ocean water increases evaporation and adds moisture to the atmosphere. At the same time, El Niño can alter the jet stream, influencing where storms travel and where heavier rain or snow may fall.

During a typical El Niño, the storm track becomes more active across the southern United States, from California and the Southwest to the Gulf Coast and Southeast. Those regions can experience more opportunities for precipitation, along with longer stretches of cloudy weather across portions of the Southern and Eastern states during the colder months.

El Niño can also favor warmer-than-historical-average conditions across parts of the northern U. S. and southern Canada. However, shifts in the jet stream can still allow episodes of cold weather.

"Warm oceans don't guarantee more storms, but they can give storms more moisture to work with," Pastelok said. "The location and intensity of the jet stream and storm track will ultimately determine where that moisture goes and the rate that it falls. That's why the evolution of El Niño will be so important for North America this fall and winter."

The competing influences of El Niño and ocean warmth will also be closely monitored during the remainder of the Atlantic hurricane season. Near-record-warm Atlantic waters can provide tropical systems with additional energy, but El Niño often increases disruptive wind shear across portions of the basin, making it more difficult for some storms to develop and strengthen.

Beyond its influence on weather, persistent ocean warmth raises the risk of marine heat waves, coral bleaching and disruptions to fisheries and other marine ecosystems. Warmer water also contributes to sea-level rise through thermal expansion and can hold less dissolved carbon dioxide, potentially weakening one of the planet's most important buffers against climate change.