Severe Weather:Severe weather refers to any dangerous meteorological phenomena with the potential to cause damage, serious social disruption, or loss of human life. Types of severe weather phenomena vary, depending on the latitude, altitude, topography, and atmospheric conditions.
Blizzard:
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Definition:
A blizzard is a severe snowstorm characterized by strong sustained winds of at least 35 mph and lasting for a prolonged period of time—typically three hours or more. A ground blizzard is a weather condition where snow is not falling but loose snow on the ground is lifted and blown by strong winds.
Picture of Blizzard: 
IN this picture it shows a blizzard because it's a storm of snow.
Tornado
Definition:A tornado is a rapidly rotating column of air that is in contact with both the surface of the Earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. They are often referred to as twisters, whirlwinds or cyclones,[1] although the word cyclone is used in meteorology to name a weather system with a low-pressure area in the center around which winds blow counterclockwise in the Northern Hemisphere and clockwise in the Southern.
Picture of Tornado: In this picture you can see it's a tornado
Hurricane
Picture of hurricane : This is a hurricane because hurricane needs large bodies of water
Definition:A hurricane is a type of tropical cyclone, which is a generic term for a low pressure system that generally forms in the tropics. The cyclone is accompanied by thunderstorms and, in the Northern Hemisphere, a counterclockwise circulation of winds near the earth's surface.
Thunderstorms:
Picture Of Thunderstorms In this picture it shows a thunderstorms
Definiton:A thunderstorm, also known as an electrical storm, lightning storm, or thundershower, is a storm characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere, known as thunder.[1] Thunderstorms occur in association with a type of cloud known as a cumulonimbus.