Unpredictable weather is an inherent risk in wilderness travel. Always come prepared.
It's impossible to know for certain what the weather will do, even on day hikes. Accordingly, a little common sense and a cautious attitude are two of the most important items you can bring with you into the backcountry.
Pay attention to developments in the sky. The shapes and movements of clouds typically foreshadow changes in the weather such as the arrival of warm fronts and cold fronts.
Warm fronts are defined as warm air masses that gradually push out and replace cooler bodies of air. Warm fronts, which move at roughly half the speed of cold fronts, rarely produce violent weather, but the precipitation they generate may linger for long periods. Warm fronts progress from thin, high-level cirrus clouds to low, dense stratus clouds:
Cold fronts involve cold air masses that wedge under warmer air pockets. Cold fronts can develop rapidly and move swiftly, causing temperatures to drop, wind directions to shift and barometric pressure to fall.
Tip: If late-day storms become a pattern during your trip, rise early each day and cover as much ground as you can during the day's more stable hours.
Altimeters: If you carry one, or wear an altimeter watch, an approaching cold front can cause your elevation reading to rise even if you're not moving. If you notice such a rise, this means air pressure has dropped (suggesting thinner air at a higher elevation). This is a hint that bad weather could be on its way.
The National Weather Service estimates that 100,000 thunderstorms take place in the United States each year. Lightning is present in all thunderstorms, since lightning causes thunder. How? A bolt of lightning causes the air around it to expand and contract with immense force, producing a shattering sound.
Over the past 30 years through 2008, the U.S. has averaged 62 reported deaths and 300 injuries per year from lightning, per the National Weather Service. A lightning strike sends an electrical current radiating through the ground over a large area. This "ground current" is usually the lethal force in storm-related fatalities.
Never take an electrical storm casually. If lightning threatens while you are in the backcountry, take immediate action:
How close is that lightning? Use your watch and time the interval between the flash of lightning and the sound of thunder. Thunder travels approximately a mile every five seconds (or roughly 1,000 feet per second). If it takes 10 seconds for the sound to reach you after a flash, the storm is two miles away. If that interval is shorter the next time, the storm is drawing closer.
By T.D. Wood
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Last updated: 10/05/2012
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