BANGOR, Maine (AP) — The warming Gulf of Maine recorded its hottest single day this summer, reaching 69.85 degrees Fahrenheit.

The reading was taken on Aug. 14 in what's already one of the fastest-warming bodies of water on the planet, but researchers at Gulf of Maine Research Institute only realized this week that it marked a new record, the Bangor Daily News reported.

That was a full degree warmer than the previous record of of 68.99 degrees Fahrenheit on Aug. 23, 2012, the newspaper reported.

To determine the gulf’s average temperature, scientists use readings taken by various methods, at multiple locations, and at different times of day.

Most of the surface temperature readings are obtained via satellites, but relative heat measurements also are obtained via buoys, aquatic gliders, ships and other means, according to Kathy Mills, a research scientist at GMRI.

Average temperatures in the Gulf of Maine were normal in the spring, but from June through at least mid-August, the gulf saw another heatwave.

Researchers have known for several years that the Gulf of Maine is heating up faster than 99% of the world’s large bodies of saltwater, scientists say. The rest of the world’s large bodies of saltwater are also warming, albeit not as fast.