Severe weather is any dangerous meteorological phenomenon 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. High winds, hail, excessive precipitation, and wildfires are forms and effects of severe weather, as are thunderstorms, downbursts, tornadoes, waterspouts, tropical cyclones, and extratropical cyclones. Regional and seasonal severe weather phenomena include blizzards (snowstorms), ice storms, and duststorms.
Various forms of severe weather
Panorama of a strong shelf cloud, which can precede the onset of high winds
The F5 tornado that struck Elie, Manitoba, Canada, in 2007
Formation of numerous waterspouts in the Great Lakes region
Wind is the natural movement of air or other gases relative to a planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heating of land surfaces and lasting a few hours, to global winds resulting from the difference in absorption of solar energy between the climate zones on Earth. The two main causes of large-scale atmospheric circulation are the differential heating between the equator and the poles, and the rotation of the planet. Within the tropics and subtropics, thermal low circulations over terrain and high plateaus can drive monsoon circulations. In coastal areas the sea breeze/land breeze cycle can define local winds; in areas that have variable terrain, mountain and valley breezes can prevail.
Cup-type anemometer on a remote meteorological station
An occluded mesocyclone tornado (Oklahoma, May 1999)
Winds are part of Earth's atmospheric circulation
RAF Exeter airfield on 20 May 1944, showing the layout of the runways that allow aircraft to take off and land into the wind