The world’s oceans reached their highest-ever average temperature in June as marine heatwaves continued to spread across much of the globe.
According to the latest mid-year bulletin by the Copernicus Marine Service, June recorded an average global sea surface temperature (SST) of 21.0°C.
This makes it the warmest June since records began.
Thus far, 2026 has been marked by persistently high ocean temperatures.
Source: Marine Copernicus EU
Between January and June, the average global sea surface temperature stood at 20.94°C, making it the second-warmest first six months of any year on record, just behind 2024.
By the end of June, around 82% of the global ocean was experiencing marine heatwave conditions of varying intensity — the second-largest extent ever observed after 2024, when about 83% of the ocean was affected.
Scientists identified several marine heatwave hotspots, including:
These regions experienced prolonged periods of above-average temperatures, with some reaching record or near-record levels.
The Mediterranean Sea remained one of the regions hardest hit by unusually warm waters.
Between January and June, the sea recorded an average surface temperature of 18.07°C, making it the third-warmest first half of the year on record.
Source: WWF Panda
Marine heatwaves affected around 98% of the Mediterranean, with roughly 80% experiencing strong, severe or extreme heatwave conditions.
In June, the Mediterranean reached an average sea surface temperature of 24.3°C.
That alone was a new record for the warmest June ever recorded in the region.
The North Atlantic experienced exceptionally warm conditions throughout the first half of the year.
About one-third of the North Atlantic experienced strong to extreme marine heatwave conditions, particularly across the central basin and waters west of Europe.
Meanwhile, the tropical Pacific matched its previous record average sea surface temperature for the January-to-June period.
June also became the warmest June ever recorded in the tropical Pacific, with an average sea surface temperature of 27.26°C, surpassing the previous record set in 2023.
Image by MS News
Lead Oceanographer for the Copernicus Marine Service, Simon Van Gennip, said the findings show oceans remained under significant thermal stress throughout the first half of 2026.
“Marine heatwaves expanded steadily throughout the period, ultimately affecting around 82% of the global ocean,” he explained.
The sustained ocean warming, he added, underscores the importance of continuous, high-resolution monitoring to better understand how ocean conditions continue to evolve amid a changing climate.
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Featured image adapted from Kellie Churchman on Pexels.