A blizzard is one of the most dangerous winter weather phenomena, defined by the simultaneous occurrence of heavy snowfall or blowing snow, sustained winds of at least 56 km/h, and visibility reduced to less than 400 metres for a minimum duration of three hours. Unlike ordinary snowstorms, blizzards combine these three criteria simultaneously, creating conditions that can be life-threatening for anyone caught outdoors and paralysing transportation networks across entire regions. The formation of a blizzard requires a powerful extratropical cyclone interacting with a mass of cold, moisture-laden Arctic air. As the cyclone intensifies, the strong pressure gradient between its low-pressure centre and the surrounding high-pressure system generates the sustained high winds characteristic of blizzards. When these winds encounter loose snow on the ground or falling precipitation, they create near-zero visibility conditions known as whiteout. Ground blizzards can occur even without active snowfall when strong winds lift previously deposited snow, creating hazardous conditions under otherwise clear skies. Blizzards are most common in the northern Great Plains of the United States, the Canadian prairies, northern Europe, Scandinavia, and the Russian steppe. In Spain, severe blizzard-like conditions occasionally affect mountainous regions of the Pyrenees, the Cantabrian Mountains, and the Sistema Central during intense cold-air outbreaks from northern Europe. These events can isolate mountain villages, close major passes, and create avalanche danger. The wind chill effect during a blizzard can lower the perceived temperature dramatically—actual temperatures of -10°C combined with 60 km/h winds produce a wind chill equivalent of approximately -25°C, leading to frostbite risk in under ten minutes of exposed skin.