LEWISTON — As far as John Grenier is concerned, it’s perfectly OK to stuff a sock down the front of your pants.

It’s going to be cold for the Dempsey Challenge this weekend and dressing warm is going to be vital for the riders Sunday morning.

“It’s probably going to be below freezing at the start of it,” said Grenier, owner of Rainbow Bicycle in Lewiston. “If you haven’t dealt with that before, it’s going to be a shock to the system.”

Weather forecasters are calling for freezing temperatures overnight and not much warmer during daylight. Lows to mid-40s are in the forecast and there’s a strong chance of rain throughout the weekend.

It’s not exactly the kind of forecast you want to hear if you plan to be out on your bicycle all day. The weekend Dempsey Challenge may be less about shorts and tank tops and more about balaclavas, mittens and neoprene.

The Challenge this year was scheduled later than usual to accommodate Patrick Dempsey’s filming schedule. He’s been filming “Bridget Jones’s Baby” in London and racing in the World Endurance Championship in a Porsche 911 RSR.

Dempsey will be here. But even the warmth of his stardom won’t be enough to keep the riders warm as they set off on the course at 7 a.m. Sunday. According to Grenier, planning for the cold will keep the riders safe and warm.

“Thinking you’ll just tough it out is not the answer,” he said. 

His advice ranges from specialty clothes to the low-budget version. The first trick is to keep the extremities warm, he said. Get something that’s windproof but which also can breathe. Moisture wicking is important on all parts of the body. Forget that ratty old T-shirt you think is lucky.

“You don’t want any cotton on your body that day,” said Grenier, who rides year-round.

Next, the head. The ears need to be covered, Grenier said, but so does the rest of the noggin.

“Most of your heat is lost out the top of your head,” Grenier said. Preventing that heat loss is half the battle.

Gloves? Something windproof with moisture wicking would be just the thing. It helps to have some sort of tactile feel for gear shifting, but it’s more important to keep those paws warm.

“Your hands are going to be out in the wind,” Grenier said. If necessary, a rider can don a regular pair of mittens, which keep the fingers together to preserve warmth.

Grenier’s Lisbon Street store has all the cold-weather gear a rider needs, but he said staying warm can be done on the cheap, as well. Find some mittens and a wool hat at Goodwill, for example. Plastic bags over the socks, a wool stocking over the sneakers, whatever. Some of Mom’s old-school remedies are still plenty effective.

“These aren’t the best solution,” Grenier said, “but they’re better than nothing.”

He advises against riding in shorts, which would be tough on the legs. And yes, nobody will be ostracized for stuffing a sock down the front of the pants to keep that part of the body warm in the rush of wind that comes with riding.

Bad weather? It depends on how you look at it.

“You know what they say: If you’re properly dressed, there’s no such thing as bad weather,” Grenier said.