#10: New Year's 1961 (Northern Idaho)
The most destructive ice storms feature heavy ice accumulation, sometimes on the order of several inches, that, when combined with strong winds, bring down trees and power lines, plunge hundreds of thousands into the dark sometimes for several days.
We've collected a list of the top 10 worst ice storms in U.S. history, starting with one in northern Idaho.
A three-day ice event ushering in 1961 featuring not only freezing rain, but also occasional freezing fog set a U.S. record ice accumulation of eight inches in north-central Idaho, according to Weather Underground's Christopher Burt (blog).
Power outages and tree damage was widespread in this area.
Incidentally, one somewhat common ice storm corridor is along the Columbia River, where subfreezing air spilling over the Continental Divide can sometimes remain trapped ahead of a wet Pacific storm.
NEXT > #9: Slippery Super Bowl