Some notable hots spots include South Africa, Australia, Europe, New Zealand, northern India, Canada, Argentina, Uruguay, and the United States. Of these locations, the United States has some specific regions within its boundaries that have an extremely high number of events per year. Figure 5t-8 describes the spatial distribution of tornado frequency in the United States. Average number of tornadoes per year in the United States. Tornado occurrence has some interesting temporal characteristics.
Tornadoes also have particular times of the day in which they form.
Most tornadoes form in the afternoon. Few develop in the late evening or early morning. During these times, heating of the Earth's surface is minimal or not occurring. Intense heating enhances updrafts in severe thunderstorms. It is these updrafts that can cause a tornado to form.