Coping with Cold Weather
1988
by John Ohrt
With cold weather coming upon us, now is a good time for a reminder about special considerations for cold-weather paddling. This article is re-printed from a 1988 HCC newsletter article, written by John Ohrt 27 years ago, but is still just as valid today.
The human body tries to maintain itself at a temperature of about 99°F. if the body gives up any heat to the environment it feels "cold". One way to look at the problem of being cold, is to think in terms of the presence or absence of heat. Cold is the name we give to the absence of heat, and to stay warm we must study the ways our bodies lose heat to the environment, and learn techniques to prevent this loss. Body heat is lost by radiation, convection, conduction, evaporation, and respiration.
Radiation is the loss of heat from a bare surface. This
is the principle that explains why the coldest nights are the
clear ones.
Our unprotected bodies radiate heat into the environment, and this must be prevented by wearing insulating clothing. One area that is often overlooked is the head.
The uncovered head can lose up to 1/2 of the body's total heat production
at 40° (3/4 at 5°), so it is essential to carry and wear a warm
hat in cold weather. One should even sleep with a hat on very
cold nights for extra warmth. There is an outdoor saying, "
If your feet are cold, put on a hat". While I have never found this
to be exactly true, it points out the idea that by preventing
sizable heat loss from the head, you save that heat for other
parts of the body. A warm hat should be standard equipment on
any winter trip.
Convection is loss of heat from the body to moving air
(wind).
In the outdoors wind is one of your greatest enemies,
quickly stealing body heat and energy. Our bodies warm a thin
layer of air next to the skin, and it is a primary function of
clothing to retain this warm layer of air.
If wind constantly
removes this warm layer, we feel cold.
The extent of this can
be seen on a wind chill chart. If the temperature is 40° with a
15 MPH wind, it is effectively 22°.
This wind chill vastly
increases if the body or clothing is wet.
Being wet in a cold
wind is a seriously dangerous situation that must be recognized
and dealt with quickly. Windproof outer clothing protects
against convection. Also one can use rocks, walls, bridge supports, and even canoes as wind breaks.
Do not underestimate
the power of wind in accelerating heat loss, and do whatever
you can to protect yourself in windy conditions.
Conduction is heat lost from direct contact with a cold
surface (
rocks, metal, water, etc). An example of this would
be sleeping without an insulating pad underneath you, which can
feel as if your body heat is flowing directly into the cold ground.
Because of this principle, it is best not to have direct,
uninsulated contact with surfaces colder than your body. Another
example would be a passenger sitting on the bottom of an aluminum
canoe. The direct contact with the cold water, through the metal,
would cause this person to lose lots of heat quickly. Also, if
your sleeping pad is not full length, make sure that your feet are
up off the ground, or else they could become cold through conduction.
Be aware and creative in insulating yourself from colder objects.
Waterchill
is a particularly dangerous form of conduction,
because the thermal conductivity of water is 240 times as great
as that of still air. Water of 55° can extract heat from your
body up to 240 times faster than 55° still air. This is why dry
suits, wet suits, and pile or wool clothing are worn in cold
water conditions, even if the air temperature is quite warm.
Also be aware that clothing, especially down and cotton, loses
insulating value when wet. Wool and synthetics are the clothing
of choice for wet conditions.
Be especially careful of any
situation that can combine wet clothing with a cold wind, as this
can cause you to lose more heat than you can produce and lead to
hypothermia.
Evaporation is heat loss from evaporation of sweat or
moisture on the skin. This loss can be significant, but about
all you can do about it is to adjust your pace to avoid excess
perspiration. If you work too hard, you can produce too much
sweat, which can soak your clothes and cause you to become
chilled when you stop exercising. Take off clothes, open vents,
and adjust your pace to prevent this from happening. In extremely
cold conditions, perspiration can condense and freeze in outer
garments or sleeping bags causing them to become very heavy
This principle can be reversed in the summer by pouring water
over you and being cooled by the subsequent evaporation.
Respiration is the heat loss caused by inhaling cool air
and exhaling warm air.
There is not much you can do to prevent
this type of heat loss.
Breathing is not optional.
Remember that openings in clothing can lose a lot of heat,
especially with the pumping motion caused by exercise.
Buttoning
the top button of your shirt, closing up zippers, and tucking in
shirttails, can conserve a great deal of heat.
The head and the
back of the neck are also very vulnerable to cold, so wear a
warm hat and turn up your shirt collar or wear a turtleneck or
a scarf to protect these areas. Food is a source of energy and
heat, so eat regularly and well; drink plenty of water also, to
avoid dehydration. Don't overlook external heat sources such as
fire and hot liquids. A quick fire can perk you right up on a
chilly day, and a butane lighter, waterproof matches, and wax-paper for starter make a good fire kit.
I have even seen flares
used to start bankside fires. Hot liquids can be carried along
in thermos bottles.
A waterproof rain suit that can double as
wind protection should be considered required equipment in the
winter. Remember that shivering is the body's response to cold,
and while it produces heat for the body, it also uses up a lot
of energy and can wear you down to dangerous levels. Shivering
is a sign that you are too cold and need to warm up. Try to
dress in several layers of loose clothing to trap insulating air;
tight fitting clothes block blood supply and heat. Avoid cotton
and rely on wool or synthetics for protection in cold, wet conditions.
Pay attention to the weather forecast, and take the necessary equipment, plus enough extra to handle a little worse weather
than is expected
This safety cushion should see you through any
sudden weather shifts.
You can always take clothes off, but you
can't put them on if they're left at home or in the car. In
Texas the winter weather can change dramatically; drops of 20°
over two hours with high winds and hard ain are not uncommon.
Go on trips prepared for the cold, and be alert to changing
weather conditions and heat loss in yourself and your companions.
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The author, John Ohrt.
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