January 1998 North American ice storm

The North American Ice Storm of 1998 (also known as the Great Ice Storm of 1998 or the January Ice Storm) was a massive combination of five smaller successive ice storms in January 1998 that struck a relatively narrow swath of land from eastern Ontario to southern Quebec, New Brunswick and Nova Scotia in Canada, and bordering areas from northern New York to central Maine in the United States. It caused massive damage to trees and electrical infrastructure throughout the area, leading to widespread long-term power outages. Millions were left in the dark for periods varying from days to several weeks, and in some instances, months. It led to 34 fatalities, a shutdown of activities in large cities like Montreal and Ottawa, and an unprecedented effort in reconstruction of the power grid. The ice storm led to the largest deployment of Canadian military personnel since the Korean War, with over 16,000 Canadian Forces personnel deployed, 12,000 in Quebec and 4,000 in Ontario at the height of the crisis.

Background

Freezing rain is common in the eastern half of Canada and New England, generally occurring at the narrow boundary between cold air from the east and north and moist air from the south. Typically, a warm air mass will travel northward along the Mississippi Valley and overrun a shallow layer of cold air trapped at the surface. Such a favorable cold air damming happens with an east to northeasterly flow in the St. Lawrence (the predominant wind direction in the St. Lawrence Valley is usually either northeast or southwest) and the Ottawa Valley and along the axis of the Appalachian Mountains.