In the United States have more tornadoes than any other country: about four times the estimated occurring in Europe, excluding waterspouts. This is mainly due to the unique geography of the Americas. North America is relatively large and extends from the tropics to the Arctic areas, and has no major mountain chain that goes from east to west and block air flow between these two areas. In the mid latitudes, where most of the tornadoes, the Rocky Mountains block moisture and atmospheric flow, allowing drier air exists at intermediate levels of the troposphere, and causing the formation of a low pressure area to east of those mountains. An increase in the flow of air from the Rockies favors the formation of a dry line if the flow is strong at higher levels while the Gulf of Mexico, east, provides abundant low level moisture from the atmosphere. This unique topography causes many collisions of warm air with cold air, which are the conditions that create strong and lasting storms. A large portion of these tornadoes form in that area in the center of the United States between the Rockies and the Gulf, known as Tornado Alley ("tornado alley"). This area also includes parts of Canada, mainly in Ontario and the Canadian prairies, although southeastern Quebec, the interior of British Columbia and western New Brunswick are also prone to tornadoes. Sometimes tornadoes are also strong in northeastern Mexico.

On average, in the United States about 1,200 tornadoes occur each year. The Netherlands reported the highest number of tornadoes per area of any country to register there more than 20 tornadoes, which equals 0.00048 km2 tornadoes per year, followed by the United Kingdom presented annually about 33, ie 0, 00,013 per km2; However, most are small and cause little damage. In absolute numbers, regardless of territorial extension, the UK experiences more tornadoes than any European country, excluding waterspouts.

Tornadoes kill an average of 179 people per year in Bangladesh, by far the largest amount in a country in the world. This is due to its high population density, poor quality of buildings, lack of knowledge about security measures to combat the tornadoes and other factors. Other countries in the world with frequent tornadoes include South Africa, Argentina, Uruguay, southern Brazil, Australia and New Zealand as well as portions of Europe and Asia.

Tornadoes are most common during the spring and less during the winter. Since the spring and autumn are transitional periods (warm to cold weather and vice versa) is more likely that the cold air is warm air , which causes for these stations are experienced peaks. However, the conditions for its formation can occur at any time of year. Tornadoes can also be generated from the eye of tropical cyclone landfall, which often happens in the fall and late summer.

The incidence of tornadoes is highly dependent on time of day, due to solar radiation. Worldwide, most tornadoes occur during the afternoon, between 3:00 pm and 7:00 pm time local, being the highest point at 5:00 pm. However, destructive tornadoes can occur at any time of day. The Gainesville tornado of 1936, one of the most devastating tornadoes in history, occurred at 8:30 am local time.

There Jola Mediterranean) in turn increases the amount of moisture in the atmosphere. The increased moisture can cause an increase in the occurrence of tornadoes, especially during the cold season.

Some evidence suggests that the phenomenon Southern Oscillation (ENSO, for its acronym in English) is slightly related to changes in the activity of tornadoes, this varies by season and region and depending on whether the phenomenon ENSO corresponds to that of El Niño or La Niña.

Climate change may affect tornadoes through teleconnections as when changing a jet stream and other major weather patterns. Although it is possible that global warming might affect the activity of the tornadoes, this effect can not yet be identifiable because of its complexity, the nature of storms and issues relating to the quality of databases. In addition, any effect would vary by region.