Real bikers ride in the winter, too. Frostbite is a danger. The likelihood depends on: the temperature (of course), the speed of your bike or the wind, the insulation provided by your clothing, and whether you're in contact with snow or water. Waterproof shoe covers are available for winter biking (they have an opening at the bottom for your cleats).
Description:
Frostbite is an injury to your cells caused by freezing. It may involve only the skin, but
can also damage deeper tissues like arteries, nerves, or muscles. It often resembles a
burn in appearance.
Frostbite can hit your nose, ears, or cheeks from biking in freezing wind. Even a thin headband usually prevents frostbite of the ears. It will fit nicely under your helmet. If the temperature is below 20 F, consider a facemask (just like you use for skiing).
Frostbite commonly hits fingers because: (1) as you grip the handlebars, you reduce blood flow to the fingers, (2) they're out there in the wind, and (3) they get wet from the blowing snow or rain. (Insulated biking gloves are available, and certainly help when biking is sub-freezing weather, but you can still get frostbite through them.)
Frostbite of the toes is usually the result of riding through water when the air is below the freezing point. Shoe covers keep splashing water from filling your shoes. Winter mountain-biking shoes are available, but they're expensive. I recommend using your roomiest shoe with shoe covers and double socks (wool or acrylic rather than cotton).
Concerns:
Clotting in damaged blood vessels can increase the amount of tissue death -- perhaps even
to the point of amputation. The deep tissue damage sometimes causes chronic pain and cold
sensitivity. And like a burn, frostbite has some risk of infection.
Warm the cold numb area. Use water that's about as warm as a mild bath. If the area remains numb and pale, go to the hospital.
Ongoing care:
The area may blister. If so, treat it as you would a second-degree burn. Leave the
blisters alone. Bandage. Expect about 10 to 14 days to heal. Watch for signs of infection.
Scenario:
Whereas frostbite is the result of freezing injury of a small body area, hypothermia is
the gradual cooling of the body. The risk is greatest, not in the dead of winter, but when
cold is unexpected. For example, a biker caught with a flat tire at 10,000 feet when a
wind-driven rain hits.
Description:
Your nerves and muscles function only within a narrow temperature range. Once the body
temperature drops 5 degrees F, confusion and weakness develop. Shivering stops.
(Hypothermia victims often feel warm and remove clothing during this stage.) As the
temperature reaches 10 degrees below normal, consciousness is lost. Death occurs a few
degrees later.
Immediate care:
Stop the victim from getting colder. Get the wet clothing off and replace it with dry. If
you have a hypothermia blanket, use it. If not, any barrier to wind and wet will help. Get
to a hospital as quickly as possible.
If you can't get back to civilization, get to a sheltered area and start a fire. Heat up your bike water bottles and stick them inside the clothing. If the victim can swallow, drinking warm water can help.
A plastic waterproof rain slicker costs around a dollar. It can sit in your biking backpack until you need it to keep the rain off you. Remember, it isn't the cold, it's the wet and cold that kills you. A hypothermia blanket is a tough foil-covered plastic that's also surprisingly light. The foil reflects back body heat. And you can't generate heat unless your body has energy, so a high-calorie snack completes the hypothermia preparation.
