I intend to take the Route Napoleon in mid April and I'm still unsure how much warm gear I'll need. Recent weather reports for St Jean PP indicate daytime ambient temperatures in the 12C - 15C range. Usually a merino base layer and 2 thin synthetic top layers are enough for me at that temperature (as long as I keep moving!). However, I'm wondering if I'm going to feel the cold if there is still snow on the ground up on the mountain and the sunlight is reduced by fog...
The advice on layering is a biggie. You never dress with the amount of clothing needed to keep you warm at the start of walking or hiking... you wear the amount of clothing needed to keep you warm 10 minutes after you start walking.
In cold weather, or even cool weather, one needs to do what is necessary to prevent overheating and sweat. That includes how fast a pace one is moving at in exerting energy, as well as how much clothing one is wearing, and how much air circulation one is able to maintain.
It does not take long, with any layering amount, to saturate clothing with sweat. THAT is when the danger of hypothermia, and at the very least a chilly discomfort will begin to take its toll. If saturation or wetness happens, the only recourse is to change into dry clothing. Since there is usually a limited amount of clothing carried in a backpack, it is essential to adopt strategies to control sweating.
Keep in mind that the material of your layers will also determine the effect to you from the above scenario. Focus on clothing made from merino wool or specialized synthetics. These will allow the garment to remain somewhat insulative even though saturated with sweat. Cottons and cotton blends are a menace and can accelerate a hypothermic condition.
Strategies include those mentioned above:
- Limit layers of clothing to only those needed when full exertion is going to be achieved. For those who can't suck it up
for a few minutes, then wear only layers which can be quickly and easily removed. For instance, adding a poncho will add about a 15 degree F advantage to existing layers. It allows for good air circulation. As you warm up during the first 10 minutes of your walk, the poncho is easily removed and stashed into a side pocket of your pack.
- Move as slow as you need to, within reason, to keep perspiration to a minimum. This may also mean stopping to allow your body to cool down. Even with a single, lightweight layer, some folks walking under load will tend to over-heat. Keep monitoring yourself.
- Keep an insulative layer near at hand so that if you are wetting-out while walking, you can put it on quickly when you stop for a break. Keep it in an outside pocket or on top of the other contents in your pack. A light puffy jacket or mid-weight fleece or a down vest works well here. The key is to keep this layer dry and to use it as a last resort when at rest. If this strategy is needed, do not continue walking until you have been able to stop sweating and you can achieve some level of dryness to your clothes.
In the above scenario, you may actually become warmer by removing your saturated layers so that you only have on your dry insulative layer. Dig out a towel and dry off excess sweat as best you can. Wring out your other layers and let them start to dry. If you have a second shirt, put it on. Hang your wet things from your pack so that they can dry. After you have cooled down, and with your dry layer and your insulative layer on, walk slowly to avoid re-heating. You will make progress down the path, stay warm, while letting your wet layers become dry. The real goal at this point is to dry your layers, not achieve distance.
- Do not discount the amount of added warmth a light scarf or bandanna or a buff will bring as it insulates your neck. Wearing one can make wearing less layers very comfortable. It will also be a good first line of defense against over-heating and excess sweating by the ability to remove it, thus allowing the neck to act as a radiator in helping to shed body heat.
- Yes, the type of head gear worn makes a big difference in one's body's heat loss or retention. A hat that works well for sun is not going to be the best choice for cold weather. Wool is king, as it is far less impacted by sweat affecting its inuslative properties than most other materials. And even though wool weighs more than other types of insulation, you do not need a heavy cap of wool to keep you warm. Wool is also far more breathable than many materials which aids in heat control.
As with neck wear, a wool cap can be easily removed to assist with cooling the body to prevent overheating.
Much of the above is what I have used when mountain climbing at high altitudes. Patience and light, multiple layers is the key to preventing hypothermia when being active outdoors.
I'm aiming to finish on May 20th.
