It took just a bit over an hour of walking this morning to develop this cool frost layer. It was -5°F and about 5mph wind but I was comfortable the whole time.

At -10°F, it takes about 30 minutes to get frostbite on exposed skin, but less than 15 minutes at -20°F. Above about 15°F, there is much less concern about frostbite, but hypothermia remains something to watch for as people slowly lose their core body heat over hours, not minutes.

Keep these points in mind to prevent frostbite:

• Keep Moving - muscle activity keeps warm blood flowing to your extremities. Sitting, or even standing in one position, can reduce circulation which increases frostbite potential. Don't move so much that you sweat and get your clothes wet.
• Wear loose layers - this provides dead air space which means more insulation. A big fleece crushed under a tight-fitting windbreaker loses loft - wear an oversized outer layer.
• Cover up - Exposed skin freezes fast so cover everything but your eyes.
• Convection cools - a 0 degree windless day is less dangerous than a 15 degree day with 15mph wind. A windproof outer layer makes a big difference. Even a thin wind/rain jacket hood over your stocking hat helps a lot.
• Winter Gear - a scarf or balaclava protects the face; mittens instead of gloves keep fingers together and warmer; insulated boots, especially with thick soles, keep feet warmer than hiking boots. Chemical heat packs in boots and mittens can be a big help.
• Limit Exposure - if you expect frostbite temperatures for your outing, plan a shorter hike or use shelters along the way to warm up occasionally.

Hike On!