Cyclist Gary Helfrich gauges how cold the winter morning is by how much his water bottle freezes as he pedals to work from the west county to Santa Rosa.

"So far this year there's been mostly a crust on it," he said, "but one time is was frozen all the way through."

As executive director of the Sonoma County Bicycle Coalition, Helfrich's preferred mode of transportation is no surprise, but his all-weather desire to go by bike might be, especially to those who think winter calls for staying cozy indoors.

"Most people think I'm nuts," said Helfrich who used to bicycle year-round in New England before moving here.

Helfrich is one of those winter people who doesn't let temperatures or precipitation get in the way of doing what they love. But how do such hardy souls stay healthy? And dry and warm?

Helfrich, who's found it's better to be wet than cold, opts for clothing designed for mountaineering and skiing over bicycling gear. That includes a jacket "that fits loose and flaps in the wind, which lets you layer up underneath." Plus thermal skiing underwear, which is "way cheaper than bike tights and a lot warmer." He wears a polypropylene beanie under his bike helmet to wick moisture, open-air sandals because they drain and polypropylene socks "that get soaked but will keep your feet warm."

"If you get cold, you're not wearing the right base layers," said Helfrich, who lives in Camp Meeker but cuts his winter commute short by starting in Graton.

"I don't have the nerve to ride Graton Road in the dark."

Santa Rosa dentist Conrad Block says winter is one of the best times to surf, which he does most weekends at Marin County's Dillon Beach.

In winter, he said, "the swells come in more frequently and are a little bigger, but the weather is often better for surfing because the wind is not up or is blowing offshore."

He wears the same wetsuit year-round but has a warm-up technique for winter. Before leaving home he heats up his wetsuit in the clothes dryer and wraps it in warm towels so it's still toasty when he gets to the beach.

He brings along three gallons of hot water to pour inside his wetsuit before grabbing his board. After a couple hours of surfing he gets under a long robe so he can wiggle out of his wetsuit on the beach and get into his fleece-lined jeans, turtleneck and hoodie.

Then he's off in his car with the heated seat to join his surfing buddies in Valley Ford for a hot toddy and oysters.

Block's health regimen includes taking Vitamin D and fish oil supplements and working out at the gym.

"Colder days do make you get tired a little faster," he said. "The days my teeth are chattering I won't last as long in the water. But I'll go out no matter if the wind is blowing and it's raining."

Alisa Proudfoot of Windsor is a self-described "winter person" who started skiing when she moved to Nevada City in the sixth grade.

"I don't really like the heat," she said. "I prefer cold."

Proudfoot started out the new year with four sub-freezing days at Tahoe where she skis weekends and works at Sugar Bowl ski resort as a mountain safety volunteer.

When the temperature is in the single digits, she wears a down jacket underneath a ski jacket. She favors mittens over gloves, starts with a hand warmer insert, then adds a liner mitten and a waterproof mitten.

She wears a fleece balaclava under her ski helmet to cover her head and neck, plus polyester tights and wool socks.

"Lots of layers and wool is best," said Proudfoot. "Everything I wear wicks away moisture."

To protect her skin from the mountain air, she uses a petroleum-based moisturizer under sunscreen. To keep healthy she takes Emergen-C vitamin supplement, drinks lots of water and gets a flu shot.

She begins her ski mornings with an egg and cheese sandwich and ends them with a fireside glass of wine at the Santa Rosa Ski Club's cabin in Truckee, which she calls her "winter home."

Cyclist Helfrich says winter people enjoy elements of the season that the house-bound miss.

"I feel like everyone inside is isolated from nature," he said, describing his ride home "on a cool cloudless night when the stars are so bright."

It's not always wondrous.

"The absolute worst point is getting a flat and it's 8 p.m. in February and raining an inch an hour. You have to take your gloves off to fix the tire and as soon as you stop pedaling you get really cold."

That's when he pulls out his cell phone and calls home, to ask his wife to come get him.

Susan Swartz is a freelance writer and author based in Sonoma County. Contact her at susan@juicytomatoes.com