Global Ocean Temperatures Hit Highest Level in Recorded History, Even as Summer Should Be Cooling Seas

The global ocean's average surface temperature reached 21.104 degrees Celsius (69.99 degrees Fahrenheit) on August 22, the highest daily reading ever recorded, surpassing the previous record of 21.09 degrees Celsius set in March 2024. The milestone is unusual because the Southern Hemisphere's winter typically causes global ocean temperatures to cool through August, not climb to new records.

Scientists point to an unusually strong El Nino, which began in June, as the main driver. According to Berkeley Earth, the odds that 2026 will end up the hottest year on record have jumped from around 12% in July to 69% in August. Researchers describe the event as acting like a preview of temperatures the planet might not otherwise reach for another decade.

The heat has already had visible effects on land: rivers across Europe, including the Rhine, have dropped to their lowest recorded levels amid extreme heat and drought, straining shipping and agriculture across the continent.