Marine heatwave Bulletin
Forecasts for 4 October 2025​

European Zone

 

Mediterranean Sea

Marine heatwaves in the Mediterranean Sea are decreasing in intensity and extent. Both basins are affected by only moderate categories. 

Global Ocean

 

North Tropical Atlantic

The marine heatwave in the Gulf of Mexico and in the Caribbean Sea is intensifying with a greater proportion of strong categories and locally severe. North of the Antilles, the area of the marine heatwave has diminished. The marine heatwave extent around 30°W and near the equator is stable but its intensity is increasing, and is now mainly in strong category. 

North Pacific

The marine heatwave between the Japanese and North American coasts is decreasing in extent between 160°E and 120°W. Its intensity increases globally with a greater cover of the area by strong categories, except around 150°E where it decreases in moderate categories. The marine heatwave in the Yellow Sea, in the East China Sea as well in the Japan Sea is increasing in size and intensity, with mainly strong to severe categories, and locally extreme. 

Tropical Pacific

The extent of the marine heatwave around Papua New Guinea and Indonesia is increasing, while its intensity is stable, with moderate and strong categories.

Indian Ocean

The marine heatwave in the Bay of Bengal is decreasing in extent but remains in the moderate category. Around the equator, a marine heatwave of strong to locally severe categories spreads from the coast of Sumatra to around 65°E.