Global oceans hit hottest June on record at 20.98°C, with El Niño set to intensify warming

A new June record

The global sea surface temperature averaged 20.98°C in June 2026, according to the European Copernicus Marine Service. That surpassed the previous June record of 20.89°C, set in 2024. The first half of 2026 now ranks as the second-warmest January–June period on record for the oceans, trailing only the first six months of 2024.

Carlo Buontempo, director of the Copernicus Climate Change Service, said the conditions may point to a new phase of warming.

The current conditions could indicate the start of a new phase, taking us, once again, into uncharted territory.

El Niño's return amplifies the heat

The central and eastern equatorial Pacific, the region most directly affected by El Niño, saw the strongest anomalies. The tropical Pacific recorded its warmest first half-year on record, averaging 26.91°C and edging past the previous record from 2016. El Niño, a natural climate pattern that warms surface waters, is expected to develop into one of the strongest events ever observed by the end of 2026.

With the arrival of an El Niño year, we can expect 2026 to be among the warmest years on record.

Van Gennip, an oceanographer at Mercator Ocean International, added that it is still impossible to say exactly how much warmer. In 2024, the last year marked by El Niño, the average sea surface temperature reached a record 20.9°C before easing slightly in 2025.

Widespread marine heatwaves

Since the start of 2026, 82% of the world's oceans have experienced marine heatwaves. Nearly half of the ocean surface has been exposed to severe heat stress. The oceans absorb about 90% of the excess heat generated by human activities, mainly from burning oil, gas and coal, making them a powerful buffer for the climate system but also a driver of extreme weather.

90% of this heat is absorbed by the oceans. So if we see what 10% extra heat does to the atmosphere, imagine those 90% for the ocean.

Regional hotspots and risks

The English Channel was 5°C above the seasonal norm. The North Atlantic had just come off four consecutive months of record warmth. In the Mediterranean, 80% of the basin experienced severe marine heatwaves. Van Gennip warned that a warmer Mediterranean could intensify autumnal storm systems, including the violent cévenol and Mediterranean episodes that bring sudden, torrential rainfall to southern Europe starting in September.

Outlook for the rest of 2026

With ocean heat already at record levels for June and a powerful El Niño event taking shape, the Copernicus team and independent oceanographers expect further temperature records to fall before the year ends. Buontempo noted that the combination of background warming and El Niño makes additional records likely, though the exact magnitude remains uncertain. The persistent heat underscores the accelerating pace of ocean warming driven by greenhouse gases.