SAN DIEGO - It’s 72 degrees and sunny, the way it usually is here. In a city full of golf courses and beaches, Mike Pierce is spending his afternoon ... in a commercial freezer?

The 42-year-old is training for the Antarctic 100K on Dec. 15, so he needs a place that’s really, really c-c-cold to prepare for the ultra marathon, which will cover 62.1 miles on the f-f-frozen continent on the bottom of the planet.

Two or three times a week, he heads down the freeway from his suburban home to a cold-storage warehouse and heads for freezer box No. 9.

There, in a 60-by-40-foot space, among pallets of frozen food piled to the ceiling, with fans blowing in frosty air and the thermometer hovering around minus-5, he can simulate all the discomforts of Antarctica, minus the ice and rock.

Of course, most people think he’s crazy.

“The truth of the matter is, while it may appear that way, I really like this. I’m very focused on what I’m doing for the specific reason of going to the Antarctic and accomplishing what I want to do,” Pierce said during a break in training. “This is the way to get there.”

Pierce has been a fan of Antarctic history and its explorers since he was a kid. As a motivational speaker, he uses stories of those explorers’ difficulties to explain business principles, such as dealing with sudden and unexpected changes.

“I am a runner, but I’m also driven by going to the Antarctic and experience what these explorers did,” he said. “I came looking for more than a marathon.”

Pierce encounters his own Antarctic-like difficulties while working out in the freezer. Depending on how full it is, he’ll run, ride a stationary bike or jump rope. An hour or two is a short workout. He said he spent 24 straight hours pedaling in the freezer in June. He’s also done a marathon in the freezer — running from wall to wall in 4 hours, 40 minutes.

His routine sometimes is interrupted when a worker brings in another pallet on a forklift.

“I don’t know what I’m running by in here,” he said. “There’s all kind of pizzas and burritos and plasma and who knows what,” said Pierce, who’s writing a book, Antarctic Moments, and has become known among the extreme-athlete set as “Antarctic Mike.”

On Tuesday, he was running laps around pallets of apple and pumpkin pies.

Pierce comes from a triathlon and half-marathon background. He ran the first Antarctic Ice Marathon in January, finishing last in a field of nine in 7 hours, 10 minutes.

“Normally in a race, people measure their progress by what time they did or if they beat somebody, or something like that,” he said. “This race is totally different. It was a mind-set of, if all nine start and all nine finish, we’ve all come away with a gold medal. I really felt like an Olympic champion when I was done.”

The next day, he ran the course again, covering the 26.2 miles in about 8 hours.

Race organizer Richard Donovan ran the first Antarctic 100K in January in a time of 15 hours, 43 minutes, 55 seconds.

Pierce will be running 62.1 miles for the first time and figures it will take him from 18 to 22 hours, depending on the wind.

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When he trains in the freezer, he wears about 80 percent of the gear he’ll don in the race, including a base layer from his sponsor, Duofold. He also wears a fleece layer, a Gortex outer layer, gloves and a stocking cap. In the race, he’ll also wear goggles.

“No skin’s exposed,” he said.

“It’s like running 60 miles on a beach in the thick sand,” Pierce said. “The difference is, you drop the temperature, if you’re here in California, by about 70 to 80 degrees, and you add about a 30-knot wind. The snow is real fine. It’s really dry, so it’s like sand.”

At least there’s no danger of tripping over a penguin.

“We’re about 250 to 300 miles inland; the penguins go only about 70 miles because they have to be in proximity to the ocean,” Pierce said. “So there’s no life — plants, bugs, animals, nothing where we are. Just ice and rock.”