The water temperature at the tip of Florida has hit hot tub levels, exceeding 37.8 degrees for two days in a row.
Meteorologists said it could potentially be the hottest seawater ever measured, although there are some issues with the reading.
Just 26 miles (40km) away, scientists have seen devastating effects from prolonged hot water surrounding Florida – devastating coral bleaching and even some death in what had been one of the Florida Keys’ most resilient reefs.
Climate change has been setting temperature records across the globe this month.
Weather records for seawater temperature are unofficial, and there are certain conditions in this reading that could disqualify it for a top mark, meteorologists said.
But the initial reading on a buoy at Manatee Bay hit 38.4 degrees on Monday evening, according to National Weather Service meteorologist George Rizzuto.
On Sunday night the same buoy showed an online reading of 37.9 degrees.
“It seems plausible,” Mr Rizzuto said. “That is a potential record.”
While there are no official water temperature records, a 2020 study listed a 37.6 degrees mark in Kuwait Bay in July 2020 as the world’s highest recorded sea surface temperature.
Mr Rizzuto said a new record from Florida is plausible because nearby buoys measured in the 36.7-37.2 degrees range.
Yale Climate Connections meteorologist Jeff Masters said: “This is a hot tub. I like my hot tub around 100F/101F (37.8/38.3 degrees). That’s what was recorded yesterday.”
Hot tub maker Jacuzzi recommends water between 37.8 and 38.9 degrees.
“We’ve never seen a record-breaking event like this before,” Mr Masters said.
But he and University of Miami tropical meteorologist Brian McNoldy said that, while the hot temperatures fit with what is happening around Florida, it may not be accepted as a record because the area is shallow, has sea grasses in it and may be influenced by warm land in the nearby Everglades National Park.
Nevertheless, Mr McNoldy said: “It’s amazing.”
The fact that two 100F measurements were taken on consecutive days gives credence to the readings, he said. Water temperatures have been in the upper 90s in the area for more than two weeks.
There are not many coral reefs in Manatee Bay, but, elsewhere in the Florida Keys, scientists diving at Cheeca Rocks found bleaching and even death in some of the Keys’ most resilient corals, said Ian Enochs, head of the coral programme at the National Oceanic and Atmospheric Administration Atlantic Oceanographic and Meteorological Laboratory.
NOAA researcher Andrew Ibarra, who took his kayak to the area because of the hot water, said: “I found that the entire reef was bleached out. Every single coral colony was exhibiting some form of paling, partial bleaching or full out bleaching.”
Some coral had even died, he said.
This is on top of bleaching seen last week by the University of Miami as NOAA increased the level of alert for coral problems earlier this month.
Until the 1980s coral bleaching was mostly unheard of around the globe yet “now we’ve reached the point where it’s become routine”, Mr Enochs said.
Bleaching, which does not kill coral but weakens it and could lead to death, occurs when water temperatures pass the low 30 degrees, he added.
“This is more, earlier than we have ever seen,” he said. “I’m nervous by how early this is occurring.”
It comes as sea surface temperatures worldwide have broken monthly records for heat in April, May and June, according to NOAA.
And temperatures in the North Atlantic are off the charts – as much as 5-6 degrees warmer than normal in some spots near Newfoundland, Mr McNoldy said.
