Avalanches are a major unrecognized, weather-related hazard. A leading cause of winter recreation fatalities in he western United States, a typical avalanche unloosens some 100,000 tons of snow.
In 1910, a massive avalanche in the state of Washington pushed three steam engines and several passenger cars off a steep embankment. The plummet of nearly 150 feet killed over 100 people.
Avalanches are in general a major threat to life and limb in mountainous areas. If you are skiing, alpine or cross country, avoid long slopes greater than 30 degrees as they are most prone to an avalanche.
The number of avalanches reported in the United States is between 1,200 and 1,800. The number of avalanches that actually occur, however, are probably 100 to 1000 times that number.
The state of Colorado leads the nation in deaths from avalanches, with an average of six to eight persons lost each season. Alaska and Montana also have high avalanche tolls. Most fatalities result from people, especially skiers and snowmobilers, traveling into areas that have been posted as off-limits.
The deadliest month for avalanche victims in the United States is February. Since 1950, almost 90 persons, many of them skiers, have perished in snow slides. June, July and August, incidentally, are not fatality free. Summer snow slides in high terrain sometimes catch hikers and campers by surprise.
The Handy Weather Answer Book, Visible Ink, Detroit, 1997