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What is a blizzard?

Blizzards are severe winter storms that pack a combination of blowing snow and wind resulting in very low visibilities.  While heavy snowfalls and severe cold often accompany blizzards, they are not required.  Sometimes strong winds pick up snow that has already fallen, creating a blizzard.  Officially, the National Weather Service defines a blizzard as large amounts of falling OR blowing snow with winds in excess of 35 mph and visibilities of less than 1/4 of a mile for an extended period of time (greater than 3 hours). When these conditions are expected, the National Weather Service may issue a "Blizzard Warning".   When a less severe, but still dangerous, winter storm is expected a "Winter storm Watch" or "Winter storm Warning" may be issued.  A "Winter storm Watch" is issued in advance and means that there is the possibility of a winter storm affecting your area. Keep alert and stay tuned to TV, radio, and other sources of weather information.  A "Winter storm Warning" means a winter storm is imminent or already occurring.

What makes blizzards dangerous?

Blizzards can create a variety of dangerous conditions.  Traveling by automobile can become difficult or even impossible due to "whiteout" conditions and drifting snow. If you must drive in a blizzard, be prepared!  Make sure your automobile is properly equipped and that you have emergency supplies in case you become stranded or lost.

The strong winds and cold temperatures accompanying blizzards can combine to create another danger.  The wind chill factor is the amount of cooling one "feels" due to the combination of wind and temperature.  For instance, a strong wind combined with a temperature of just below freezing can have the same effect as a still air temperature about 35 degrees colder.  A wind chill chart may be used to estimate the wind chill factor.

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Exposure to low wind chill values can result in frostbite or hypothermia.  Frostbite is a severe reaction to cold exposure that can permanently damage its victims.  A loss of feeling and a white or pale appearance in fingers, toes, or nose and ear lobes are symptoms of frostbite.   Hypothermia is a condition brought on when the body temperature drops dangerously low. Symptoms or hypothermia include uncontrollable shivering, slow speech, memory lapses, frequent stumbling, drowsiness, and exhaustion.  Both hypothermia and frostbite require immediate medical assistance! However, low wind chill values shouldn't keep you from going outside, but encourage you be informed and dress properly.

Blizzards also can cause a variety of other problems.  Power outages can occur due to strong winds and heavy snow.  Pipes can freeze and regular fuel sources may be cut off.

Storms with Strong Winds

Sometimes winter storms are accompanied by strong winds creating blizzard conditions with blinding wind-driven snow, severe drifting, and dangerous wind chill.  Strong winds with these intense storms and cold fronts can knock down trees, utility poles, and power lines. Storms near the coast can cause coastal flooding and beach erosion as well as sink ships at sea.  In the West and Alaska, winds descending off the mountains can gust to 100 mph or more damaging roofs and other structures.

Extreme Cold

Extreme cold often accompanies a winter storm or is left in its wake.  Prolonged exposure to the cold can cause frostbite or hypothermia and become life-threatening.  Infants and elderly people are most susceptible.  What constitutes extreme cold and its effect varies across different areas of the United States.  In areas unaccustomed to winter weather, near freezing temperatures are considered "extreme cold."  Freezing temperatures can cause severe damage to citrus fruit crops and other vegetation. Pipes may freeze and burst in homes that are poorly insulated or without heat.  In the north, below zero temperatures may be considered as "extreme cold."  Long cold spells can cause rivers to freeze, disrupting shipping. Ice jams may form and lead to flooding.

Ice Storms

Heavy accumulations of ice can bring down trees, electrical wires, telephone poles and lines, and communication towers.  Communications and power can be disrupted for days while utility companies work to repair the extensive damage.  Even small accumulations of ice may cause extreme hazards to motorists and pedestrians.

Heavy Snow Storms

Heavy snow can immobilize a region and paralyze a city, stranding commuters, stopping the flow of supplies, and disrupting emergency and medical services.  Accumulations of snow can collapse buildings and knock down trees and power lines.  In rural areas, homes and farms may be isolated for days, and unprotected livestock may be lost.  In the mountains, heavy snow can lead to avalanches.  The cost of snow removal, repairing damages, and loss of business can have large economic impacts on cities and towns.

Winter Precipitation



Rain drops that freeze into ice pellets before reaching the ground.  Sleet usually bounces when hitting a surface and does not stick to objects.  However, it can accumulate like snow and cause a hazard to motorists.

Freezing Rain:

Rain that falls onto a surface with a temperature below freezing.  This causes it to freeze to surfaces, such as trees, cars, and roads, forming a coating or glaze of ice.  Even small accumulations of ice can cause a significant hazard.

Winter Regions

From the Mid-Atlantic Coast to New England...The classic storm is called a Nor'easter.  A low pressure area off the Carolina coast strengthens and moves north.  Wind-driven waves batter the coast from Virginia to Maine, causing flooding and severe beach erosion.  The storm taps the Atlantic's moisture-supply and dumps heavy snow over a densely populated region. The snow and wind may combine into blizzard conditions and form deep drifts paralyzing the region.  Ice storms are also a problem. Mountains, such as the Appalachians, act as a barrier to cold air trapping it in the valleys and adjacent low elevations.  Warm air and moisture moves over the cold, trapped air.  Rain falls from the warm layer onto a cold surface below becoming ice.

Along the Gulf Coast and Southeast...This region is generally unaccustomed to snow, ice, and freezing temperatures.  Once in a while, cold air penetrates south across Texas and Florida, into the Gulf of Mexico.  Temperatures fall below freezing, killing tender vegetation, such as flowering plants and the citrus fruit crop.  Wet snow and ice rapidly accumulate on trees with leaves, causing the branches to snap under the load.  Motorists are generally unaccustomed to driving on slick roads and traffic accidents increase.  Some buildings are poorly insulated or lack heat altogether.  Local municipalities may not have available snow removal equipment or treatments, such as sand or salt, for icy roads.

In the Midwest and Plains...Storms tend to develop over southeast Colorado in the lee of the Rockies.  These storms move east or northeast and use both the southward plunge of cold air from Canada and the northward flow of moisture from the Gulf of Mexico to produce heavy snow and sometimes blizzard conditions.  Other storms affecting the Midwest and Plains intensify in the lee of the Canadian Rockies and move southeast.  Arctic air is drawn from the north and moves south across the Plains and Great Lakes.  Wind and cold sometimes combine to cause wind chill temperatures as lo was 70F below zero.  The wind crosses the lakes, tapping its moisture and forming snow squalls and narrow heavy snow bands.  This is called "lake-effect snow."

From the Rockies to the West Coast...Strong storms crossing the North Pacific sometimes slam into the coast from California to Washington.  The vast Pacific provides an unlimited source of moisture for the storm.  If cold enough, snow falls over Washington and Oregon and sometimes even in California.  As the moisture rises into the mountains, heavy snow closes the mountain passes and can cause avalanches.  The cold air from the north has to filter through mountain canyons into the basins and valleys to the south.  If the cold air is deep enough, it can spill over the mountain ridge. As the air funnels through canyons and over ridges, wind speeds can reach 100 mph, damaging roofs and taking down power and telephone lines.  Combining these winds with snow results in a blizzard.

In Alaska...Wind-driven waves from intense storms crossing the Bering Sea produce coastal flooding and can drive large chunks of sea ice inland destroying buildings near the shore. High winds, especially across Alaska's Arctic coast, can combine with loose snow to produce a blinding blizzard and wind chill temperatures to 90F below zero!  Extreme cold (-40F to -60F) and ice fog may last a week at a time.  Heavy snow can impact the interior and is common along the southern coast.  With only brief glimpses of the winter sun across the southern horizon, the snow accumulates through the winter months.  In the mountains, it builds glaciers, but the heavy snow accumulations can also cause avalanches or collapse roofs of buildings.  A quick thaw means certain flooding.  Ice jams on rivers can also cause substantial flooding.

Winter Storm Facts

What Makes a Winter Storm?

Cold Air:
Below freezing temperatures in the clouds and near the ground are necessary to make snow and/or ice.

To form clouds and precipitation.  Air blowing across a body of water, such as a large lake or the ocean, is an excellent source of moisture.

Something to raise the moist air to form the clouds and cause precipitation. An example of lift is warm air colliding with cold air and being forced to rise over the cold dome.  The boundary between the warm and cold air masses is called a front.  Another example of lift is air flowing up a mountainside.

Winter Deaths

Everyone is potentially at risk during winter storms.  The actual threat to you depends on your specific situation.  Recent observations indicate the following:


Frostbite is damage to body tissue caused by that tissue being frozen. Frostbite causes a loss of feeling and a white or pale appearance in extremities, such as fingers, toes, ear lobes, or the tip of the nose.  If symptoms are detected, get medical help immediately!  If you must wait for help, slowly rewarm affected areas.  However, if the person is also showing signs of hypothermia, warm the body core before the extremities.

Hypothermia - Low Body Temperature:

Warning signs - uncontrollable shivering, memory loss, disorientation, incoherence, slurred speech, drowsiness, and apparent exhaustion.

Detection - Take the person's temperature.  If below 95F (35C), immediately seek medical care!  If medical care is not available, begin warming the person slowly.  Warm the body core first.  If needed, use your own body heat to help.  Get the person into dry clothing, and wrap them in a warm blanket covering the head and neck.  Do not give the person alcohol, drugs, coffee, or any hot beverage or food; warm broth is better.  Do not warm extremities (arms and legs) first!   This drives the cold blood toward the heart and can lead to heart failure.

When CAUGHT in a Winter Storm...


In A Car Or Truck:

At Home Or In A Building:

Keep Ahead Of The Storm - Listen To Weather Radio For:

Be Prepared Before The Storm Strikes

At Home And At Work:

Primary concerns are the potential loss of heat, power, telephone service, and a shortage of supplies if storm conditions continue for more than a day.

Have available:

In Cars And Trucks:

Plan your travel and check the latest weather reports to avoid the storm!

On The Farm:

Move animals to sheltered areas.  Shelter belts, properly laid out and oriented, are better protection for cattle than confining shelters, such as sheds.


DRESS TO FIT THE SEASON. Wear loose-fitting, light-weight, warm clothing in several layers.  Trapped air insulates.  Layers can be removed to avoid perspiration and subsequent chill.  Outer garments should be tightly woven, water repellent, and hooded.  Wear a hat. Half your body heat loss can be from the head.  Cover your mouth to protect your lungs from extreme cold.   Mittens, snug at the wrist, are better than gloves.  Try to stay dry.
A DISASTER SUPPLIES KIT SHOULD INCLUDE:   A 3-day supply of water (one gallon per person per day) and food that won't spoil, one change of clothing and footwear per person, one blanket or sleeping bag per person, a first-aid kit including prescription medicines, emergency tools including a battery-powered NOAA Weather Radio and a portable radio, flashlight, and plenty of extra batteries, an extra set of car keys and, cash special items for infant, elderly, or disabled family members.  Be sure to see the Family Disaster Planning and Family Disaster Supply sections!