Blizzard Conditions in Rural Iowa.
Photo Courtesy of the Mahaska County EMA

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Winter Weather: Introduction

NWS Products
Wind Chill
Cold and the Body
Staying Safe


Wintertime poses a wide range of threats to the American public. Whether it is exposure to the cold, vehicle accidents caused by slick roads, or the fires caused by the improper use of heaters, hundreds of people are injured or killed each year as a direct result of winter weather.


Winter storms range from a moderate snow over a few hours to a massive blizzard with blinding, wind-driven snow that lasts for several days. Some winter storms are large enough to affect several states while others affect only a single community.

High winds, freezing rain or sleet, heavy snowfall, and dangerously cold temperatures are the main hazards associated with winter storms. Impassable snow drifts often maroon people at home without utilities or other services for days after an event. Heavy snowfall and blizzards easily trap motorists in their vehicles and make walking to find help a deadly effort. Severely cold temperatures and wind chills during and after a winter storm can lead to hypothermia and kill anyone caught outside for too long. The aftermath of a winter storm can impact a community or region for days, weeks or even months, incurring steep economic costs.

Terms to Know:

  • Blizzard: Blowing and/or falling snow with winds of 35 mph or greater, reducing visibilities to a quarter of a mile or less for at least three hours. Winds lofting the current snow pack and reducing visibilities without any falling snow is called a ground blizzard.
  • Freezing Rain: Caused by rain falling on surfaces with a temperature below freezing. The rain freezes upon contact with the ground. Large build-ups of ice can down trees and power lines and coat roads.
  • Sleet: Rain/melted snow that has begun refreezing when it reaches the ground. Sleet tends to be softer than hail and is easily compacted. Sleet can make roads slippery very quickly.
  • Wind Chill: The apparent temperature the body feels when wind is factored into the equation. See the Wind Chill page for more information.

The chart below shows how the different types of winter precipitation are formed.

Additional Links and Info:

Winter Weather and Safety (pdf)
Centers for Disease Control and Prevention - Winter Weather is the U.S. government's official web portal to all federal, state and local government web resources and services.