SAN FRANCISCO (CBS SF) — There has been a surge in swimmers taking to San Francisco Bay, thanks to warmer water in the Pacific Ocean.

“This is the warmest year since I’ve been swimming,” swimmer Taylor Standlee said.

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According to the National Oceanic and Atmospheric Administration (NOAA), water temperatures in San Francisco Bay are hovering around 66 degrees Fahrenheit.

“It feels great to be out here swimming in the water.  It’s 66 degrees, and it’s absolutely gorgeous,” swimmer Ned Boynton said.

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The water is so warm that planners for an Alcatraz swim this weekend are advising swimmers they may overheat if they wear wetsuits.

The warmup coincides with a worldwide rise in ocean temperatures, but it’s not yet clear what exactly is causing it.

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The Bay’s water is about five degrees above average for this time of year.