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Ice storm

earth science Maturity 5-7 Next article →

An ice storm is a specific type of winter weather event. It is also known as a glaze event or a silver storm. These storms are defined by the presence of freezing rain. The U.S. National Weather Service uses a specific measurement for these events. They define an ice storm as a storm that results in at least 0.25 inches of ice accumulation on exposed surfaces.

Ice Storm by NOAA
Ice Storm by NOAA

While these storms are not usually violent, they are very impactful. They often appear to be gentle rains occurring at temperatures just below freezing.

The formation of an ice storm requires a very specific arrangement of air layers. It begins with a layer of air that is above freezing temperatures. This warm layer sits above a layer of sub-freezing temperatures closer to the surface.

Precipitation by type
Precipitation by type

As frozen precipitation falls, it melts into rain while passing through the warm air. If the precipitation refreezes while still in the air, it becomes sleet. However, in an ice storm, the liquid droplets continue to fall through the cold air near the surface. This thin layer of cold air cools the rain to a temperature below freezing without turning it into ice. This state is known as supercooling, or the formation of supercooled drops.

When these supercooled drops strike an object, the transition to ice is immediate. The drops hit things like power lines, tree branches, or aircraft. As the cold water drips off the object, it forms a slowly thickening film of ice. This creates a heavy, smooth layer called glaze ice.

A street in Elora, Ontario, after an ice storm, early 1900s
A street in Elora, Ontario, after an ice storm, early 1900s

This process turns a simple rain event into a significant accumulation of solid ice.

Ice storms occur most frequently in certain parts of the United States. Most of these storms are found in the northeastern region. However, damaging storms can move much further south than expected. In February 1994, a major ice storm reached as far south as Mississippi. This specific event caused reported damage across nine different states. While meteorologists can often predict when and where these storms will occur, some still arrive with little or no warning.

The physical weight of the ice creates massive amounts of stress on infrastructure. Just 0.25 inches of ice accumulation can add about 50 pounds of weight per line span.

Ice Storm by NOAA
Ice Storm by NOAA

This weight is enough to snap power lines or break tree branches. Even large trees can break under the heavy load. The ice can also bring down utility poles and even steel electricity pylons. Such damage can leave entire metropolitan areas without electricity for several days or even a full month.

Beyond the damage to power lines, ice storms create several secondary hazards. The weight of falling branches can block roads and disrupt transportation. The loss of electricity can cause water pipes to freeze and rupture. Furthermore, the loss of power can lead to hypothermia. There is also a serious risk of unintentional carbon monoxide poisoning during prolonged outages.

A street in Elora, Ontario, after an ice storm, early 1900s
A street in Elora, Ontario, after an ice storm, early 1900s

This occurs when people use alternative heating or cooking methods like gas generators, charcoal barbecues, or kerosene heaters in confined indoor locations.

Carbon monoxide is a gas produced when appliances burn fuel without enough oxygen. This is a common problem in basements or other enclosed indoor spaces. At lower levels, carbon monoxide poisoning causes symptoms like nausea, dizziness, fatigue, and headache. However, high levels of the gas can lead to unconsciousness, heart failure, and death. Therefore, the impact of an ice storm extends far beyond the initial freezing rain, affecting health, safety, and the stability of modern utility systems.

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File:Ice Storm by NOAA.jpg
Ice Storm by NOAA.jpg
File:Precipitation by type.png
Precipitation by type.png
File:A street in Elora, Ontario, after an ice storm, early 1900s.jpg
A street in Elora, Ontario, after an ice...
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