More Than Heavy Snow

A blizzard is not just heavy snow. The National Weather Service defines it as a storm with sustained winds of 56 km/h or more, visibility under 400 meters, and conditions lasting at least three hours. Snow can even be optional: if wind whips up snow already on the ground to those limits, that counts too.

The danger is not snow itself but the combination of cold, wind, and disorientation. Wind chill pushes effective temperatures to -40 degrees. Visibility drops to zero. People caught outside can become lost within meters of shelter and freeze.