Ice Storm

Primary reference(s)

WMO, 1992. International Meteorological Vocabulary. World Meteorological Organization (WMO). Accessed 25 November 2019.

Additional scientific description

An ice storm (also called a ‘silver storm’) is a storm characterised by a fall of freezing precipitation. The attendant formation of glaze on terrestrial objects creates many hazards (AMS, 2012).

Ice storms result from the accumulation of freezing rain, which is rain that becomes supercooled and freezes upon impact with cold surfaces. Freezing rain is most commonly found in a narrow band on the cold side of a warm front, where surface temperatures are at or just below freezing (NWS, no date).

Metrics and numeric limits

Not identified.

Examples of drivers, outcomes and risk management

Heavy accumulations of ice can bring down trees and topple utility poles and communication towers. Ice can disrupt communications and power for days while utility companies repair extensive damage. Even small accumulations of ice can be extremely dangerous to motorists and pedestrians. Bridges and overpasses are particularly dangerous because they freeze before other surfaces (AMS, 2012).

The impact of ice storms can be very significant. This is illustrated by the impact of the 1998 ice storm in Canada and the United States.

Late on 4 January 1998 freezing rain began to fall on eastern Ontario, southwestern Quebec, and southern New Brunswick and Nova Scotia, Canada. This continued for six days, ending on 10 January. These areas were pelted with 80 mm or more of freezing rain and the event doubled the amount of precipitation experienced in any prior ice storm. The result was a catastrophe that produced the largest estimated insured loss (CAD 1.44 billion) in the history of Canada (Lecomte et al., 1998).

The storm slashed across northern New York and parts of Vermont, New Hampshire and Maine in the United States, leaving a vast trail of damage and destruction (approximately USD 200 million in insured losses). Nevertheless, the damage in the United States paled in contrast to that sustained in Canada (Lecomte et al., 1998).

The combined Canadian and United States insured loss stands in excess of USD 1.2 billion or CAD 1.75 billion, as of 1 October 1998 (Lecomte et al., 1998).

In Canada, 28 deaths were attributed to the storm; in the United States, 17 people lost their lives (Lecomte et al., 1998).

According to Emergency Preparedness Canada, electrical outages in the affected areas of Canada deprived 4.7 million people or 16% of the Canadian population of power. In the United States, 546,000 people were without electricity. Thus, in both countries over 5 million people were without power (heat, light and in many instances, water) in the cold of mid-winter, which intensified the human suffering (Lecomte et al., 1998).