The water temperature near Key Biscayne, a barrier island just east of Miami, had already passed 89 degrees one morning this week. And though the ocean off South Florida was slightly cooler than the recent record highs that had stunned scientists and threatened marine life, it remained phenomenally hot.
But on this serene patch of the Atlantic Coast, it was still a summer day at the beach, when nothing satisfies quite like a dip — even when the ocean feels like a thick, simmering syrup. Almost gooey.
“I like it warm,” shrugged Niki Candela, 20, a Miami native, moments after a powerful siren warned of approaching lightning.
Few of the heat-dazed people on the largely empty beach paid it any mind. The shore, usually clogged this time of year with rotting clusters of seaweed, was pristine, no longer menaced by a huge sargassum blob that unexpectedly shrank last month in the Gulf of Mexico. The shallow water was a crystalline teal, rolling oh so gently, not a cresting wave in sight.
So the undeterred regulars, people who savor being hot and abhor the cold, came out to enjoy themselves.
“This is as close as America gets to paradise,” said Lauren Humphreys, 40, who is originally from England but splits her time between Miami and Los Angeles. There, she prefers hiking to swimming in the Pacific, which on Tuesday reached about 72 degrees by the Santa Monica Pier.
Ms. Humphreys was making her second visit to Key Biscayne’s beaches that day, having come earlier to meditate. “There’s something quite special here,” she said. “It’s peaceful.”
Off the coast of neighboring Virginia Key, measurements from the National Oceanic and Atmospheric Administration showed that the water temperature peaked at 90.5 degrees Fahrenheit on Monday, and the air temperature at 87.6 degrees. On Saturday the water temperature at that location reached 92.5 degrees, a record.
The water in South Florida is always warm this time of year, but unusually so this year, with six record-high temperatures measured off Virginia Key this month. The sea surface hit 98 degrees in some areas of Florida Bay last week; the average ocean temperature in Miami in July is around 86.
Miami’s unrelenting heat this summer has meant 16 consecutive days with a heat index at or above 105 degrees, a record, according to Brian McNoldy, a senior research scientist at the University of Miami. The National Weather Service forecast a heat index of 110 degrees on Sunday, issuing its first ever extreme heat advisory for Miami-Dade County.
At the beach the next day, the scorching sand was to be avoided at all costs. “Talk to me here, so I don’t burn my feet,” Eduardo Valades, 51, told a reporter, beckoning toward the lapping water.
The water was “really hot,” he said, “but only as soon as you go in. Once you walk 50 yards out, it feels cooler.”
“I love it,” his wife, Jennifer Valades, 50, said.
The couple moved three years ago to Key Biscayne, an affluent village of about 14,000, from California. “Here, you can literally swim for hours,” she said, though she conceded that the beach was more pleasant — “perfect,” in fact — during the mild South Florida winter, when the water temperature is more likely to be in the mid-70s. Coastal temperatures are also more moderate than those inland.
Ms. Valades said she had recently spotted six or seven manatees. Mr. Valades showed a cellphone video he recorded last month of a large shark feeding right at the shore.
“We see one every three or four days,” he said, appearing far from worried about the sightings.
This week, toweling off seemed unnecessary: No one felt cold leaving the water.
“It feels like a Jacuzzi!” Sasha Mishenina told her two friends following a brief dip. They had declined to join her.
Yet going for a quick swim still felt refreshing, with the occasional cool current swirling by and little fish darting by people’s feet.
“I’m so happy, because they said we were going to have the sargassum,” Adriana Campuzano said of predictions earlier this year, as she was gathering her stuff to leave before the looming thunderstorm. “It’s clearer than it’s been in years. Maybe in a decade.”
Ms. Candela, the Miami native, had come to the beach with three friends. The ocean felt fine, she said, though she added that sometimes with such hot water, “you think, ‘What if someone’s peeing here?’”
She and her friends laid out their towels on beach chairs under an umbrella, put music on and waded in.
“It actually feels pretty cold,” Taylor Dutil, 20, a fellow Floridian, said.
“It’s a good change,” said Benny Perez, 22, who is from Chicago, where Lake Michigan was far cooler that day.
The siren blared three more times, signaling the end of the lightning threat. Not a raindrop had fallen. The four friends stayed in the water, chatting and laughing.