World's oceans hit record heat in June as El Niño threatens further temperature spikes
Global average sea surface temperatures in June 2026 reached 20.98°C, surpassing previous records, and scientists warn that the arrival of El Niño could push ocean and air temperatures even higher in the coming months.
The world's oceans experienced their hottest June on record in 2026, according to the European Union's Copernicus Marine Service. The global average sea surface temperature for June was 20.98°C, beating the previous highs set in 2023 and 2024. This record capped six months of near-unprecedented ocean warmth, marked by prolonged marine heatwaves.
The average sea temperature for the first half of 2026 was 20.04°C, slightly below the record set in the same period of 2024. Scientists say the onset of a potentially powerful El Niño weather pattern could boost global heat in the oceans and atmosphere even further in 2026 and into 2027.
"Current conditions could indicate the beginning of a new phase, leading, once more, to uncharted territory," said Carlo Buontempo, director of the Copernicus Climate Change Service. "With ocean temperatures at these levels and El Niño on the horizon, we are likely to see more temperature records fall in the coming months."
El Niño, characterized by unusually warm waters in parts of the Pacific Ocean, releases more heat into the atmosphere and influences wind, cloud, and weather patterns worldwide. It can raise the risk of extreme weather events such as floods in Peru, droughts in parts of Africa, and wildfires in Australia. The last El Niño helped make 2024 the hottest year on record.
"With the arrival and the onset of an El Niño year... we can expect that 2026 will be amongst the warmest (ever) recorded," said Simon Van Gennip, lead oceanographer for the Copernicus Marine Service. "This is due to El Niño... but also from the warming due to the greenhouse gas emissions we continue to provide for the atmosphere."
Oceans are a key climate regulator, absorbing about 90 percent of the excess heat caused by human greenhouse gas emissions. Warmer oceans increase atmospheric moisture, fueling tropical cyclones and destructive rainfall. They also contribute to sea level rise as water expands when heated, and harm coral reefs, which can bleach and die during prolonged marine heatwaves.
In the first half of 2026, marine heatwaves affected about 82 percent of the world's oceans, the second-largest extent after 2024. The Mediterranean broke its June record at 24.3°C, surpassing previous highs set in 2023 and 2025, with 98 percent of the basin experiencing marine heatwaves in the first six months. A marine heatwave in the northwestern Mediterranean broke a record intensity measurement.
The tropical Pacific also had its hottest June on record at 27.26°C, matching its 2016 record for the January-to-June period. The strongest and most persistent warming occurred in the western equatorial Pacific and off the coasts of Peru and California.
