In the sweltering summer heat, nobody tries to cool off by jumping into a hot tub. In parts of Florida, however, that’s what the ocean has felt like. Last week, sea surface temperatures reached as high as 101.2 degrees Fahrenheit (38.4 degrees Celsius) around the state’s southern tip in Manatee Bay, according to the US National Weather Service.
“It was like there was no difference between humidity of the air and going into the water,” said Chelsea Ward of Fort Myers, Fla.
Triple-digit ocean temperatures are stunning even in Florida, where residents are used to the heat and where many retirees find refuge from cold, northern winters. Several other nearby spots reached the mid-90s (about 35C). A storm finally came through mid week, helping water temperatures drop back down in to the more temperate 80s (about 29C).
When it’s hot, the body cools down by sweating, which evaporates and releases heat. Dipping into the ocean is typically so refreshing because heat efficiently transfers from your body into the water. But as water temperatures climb, that effect diminishes and you lose less heat less quickly, according to Michael Mullins, a Washington University toxicologist and emergency medicine physician at Barnes-Jewish Hospital in St. Louis.
A hot tub – or a stretch of ocean water hotter than body temperature – reverses the transfer of heat into your body. That’s not a pleasant experience on a sizzling, humid, Florida day.
“It would feel,” Mullins said, “like you are swimming in soup.”
Recently, ocean temperatures off the western coast of Florida have been a few degrees above normal, sitting around 88 to 90 degrees (31-32C). It’s not just humans that suffer when the oceans warm. Sea corals are bleaching. They can be hurt when water temperatures rise above the upper 80s (low 30sC).
July was so hot that scientists announced a global heat record even before the month ended. Climate change is creating a hotter world, warming oceans, and making some storms more destructive. Sea surface temperatures are somewhat above average around Florida, but they are far higher in parts of the North Atlantic near Newfoundland where they are as much as 5C hotter than usual.
The extremely high sea surface temperatures recorded earlier off Florida’s southern tip were caused by lots of sun, little wind, and no storms.
“I’ve never seen temperatures 100 degrees in Florida Bay in the 21 years I’ve been in the Keys,” said Andy Devanas, science officer at the National Weather Service in Key West, Fla.
People in south Florida know the ocean doesn’t tend to offer real relief from that suffocating heat.
“You aren’t getting much cooling at all,” says David Roth, a forecaster with the National Oceanic and Atmospheric Administration’s Climate Prediction Center. “Nobody goes into the water in South Florida in the summer really except to swim, because it is comfortable to swim. But it is not refreshing.”