Marine heatwave Bulletin
Forecasts for 27 September 2025​

European Zone

 

North Atlantic Ocean

The marine heatwave affecting western Norway is decreasing in intensity and extent, and is generally downgrading in moderate category. 

Mediterranean Sea 

Marine heatwaves in the Mediterranean Sea are decreasing in intensity and extent, with only moderate marine heatwaves persisting in the western basin. 

Global Ocean

Tropical Atlantic Ocean

The marine heatwave around Cuba and in the Gulf of Mexico remains generally stable, with moderate and strong categories still in place. The marine heatwave in the center of the basin around 60°W remains generally stable, with moderate categories still predominating. A moderate to strong marine heatwave is developing off the coast of West Africa. 

North Pacific Ocean

The marine heatwave between the Japanese and North American coasts is decreasing in extent towards 150°E and 160°W, and is also decreasing in intensity along the North American coast as the severe categories disappear and it generally moves into moderate to strong categories. The marine heatwave in the Yellow Sea is decreasing in size and intensity, with the disappearance of extreme categories, but remains in the moderate to severe category. 

Indian Ocean

The marine heatwave in the Bay of Bengal is decreasing in extent but remains in the moderate category. A moderate to locally strong marine heatwave is developing off the coast of Sumatra.