One of the most severe marine heatwaves on Earth has developed off the coast of Ireland and the UK, with water temperatures as high as 4-5°C above normal.

NOAA's Marine Heatwave Watch has categorized this event as a Category 4 (extreme) marine heatwave. pic.twitter.com/mDfhZEu2KY

— Colin McCarthy (@US_Stormwatch) June 17, 2023