A blizzard is a winter storm with winds over 56 km/h, heavy snowfall, and low visibility lasting more than 3 hours. Blizzards occur when cold air interacts with regions of low and high atmospheric pressure, bringing heavy snow and strong winds that can cause whiteout conditions, sickness, damage from falling trees and power lines, and dangers from hypothermia or frostbite. The Blizzard of 1888 was one of the worst blizzards in U.S. history, dumping over 40 inches of snow with winds over 45 mph across many Northeastern states and claiming over 400 lives.