The world’s oceans have reached their highest daily average surface temperature on record, adding another warning sign to an already unusual year for the global climate.
The average sea-surface temperature across the ocean outside the polar regions reached 21.1°C on August 22, according to the European Union’s Copernicus Climate Change Service. It narrowly surpassed the previous record of 21.09°C, set in March 2024. The latest figure also broke the previous August record of 20.98°C, recorded in 2023.
The timing is notable. Ocean temperatures typically reach their global peak around March and April, following the Southern Hemisphere summer. The new record arriving in August shows how unusual the current pattern has become.
Scientists are also watching the development of a strong El Niño in the tropical Pacific. El Niño is a naturally occurring climate pattern that changes ocean temperatures and atmospheric circulation, often affecting rainfall and temperatures in different parts of the world.
The World Meteorological Organization said in July that El Niño was expected to strengthen rapidly during the coming months, increasing the likelihood of heatwaves, drought, heavy rainfall and other extreme weather in different regions.
The current ocean record, however, cannot be explained by El Niño alone.
The planet’s oceans have been warming for decades as a result of human-driven greenhouse gas emissions. The ocean absorbs more than 90% of the excess heat trapped by those emissions, making changes in sea temperature an important indicator of the broader climate system.
Warmer oceans have several consequences. As seawater heats up, it expands and contributes to rising sea levels. Higher temperatures can also increase the frequency and intensity of marine heatwaves, putting pressure on coral reefs, seagrass ecosystems and marine species.
Fishing communities can also be affected when warmer water causes fish populations to move into different areas. Changes in ocean conditions can therefore have consequences well beyond the marine environment, particularly for communities and industries that depend directly on the sea.
There can also be consequences in the atmosphere. Warmer seawater provides more heat and moisture, which can contribute to heavier rainfall and potentially strengthen some storm systems. The exact effect varies by region and depends on other atmospheric conditions.
The latest ocean record comes after a month that was also unusually warm globally. The World Meteorological Organization reported that July 2026 was jointly the warmest July on record according to NOAA, matching July 2024. Copernicus ranked it as the second-warmest July. Both agencies recorded the highest global sea-surface temperature for July.
At the same time, climate conditions have varied sharply between regions. The WMO reported heat, drought and wildfires in parts of the Northern Hemisphere, while other areas experienced heavy rainfall and flooding.
That variation is important. A global temperature record does not mean every country or every region experiences the same conditions at the same time. Climate patterns are influenced by several interacting systems, including El Niño, regional ocean temperatures and atmospheric circulation.
Scientists will now be watching whether the latest ocean temperature record remains a short-term peak or becomes part of another prolonged period of exceptionally warm conditions.
For governments, researchers and communities exposed to extreme weather, that distinction matters. The longer-term trend in global temperatures remains the central concern, while the developing El Niño could add another layer of climate variability over the coming months.
For now, the latest measurement provides another clear piece of evidence that the world’s oceans are continuing to warm and that changes taking place beneath the surface are increasingly important to understanding what happens on land.
