Tornadoes are an incredible weather phenomenon. Defined as a violently rotating column of air extending from a thunderstorm to the ground, their wind speeds have exceeded 300 miles per hour (mph). Tornadoes happen all over the world, but by far, the most frequently in the United States.

The U.S. annual average is 1,200. Canada is a distant second, with around 100 tornadoes per year. Strong to violent tornadoes (those of EF3 or stronger) do not typically occur outside the United States. The primary dangers from tornadoes are wind and wind-driven debris, causing an average 80 fatalities and 1,500 injuries annually in the U.S.
NOAA's National Severe Storms Laboratory (NSSL) Collection, May 24, 2004, Credit VORTEX II
No Rules Followed
The first rule to remember about tornadoes is that tornadoes don't always follow rules. Life safety depends on knowing the facts. Those who believe that tornadoes only happen in certain places or at certain times of the year or day, could be dead wrong.

Tornadoes have been confirmed in every state in the U.S. though most frequently in the Midwest. They happen in every month of the year and though they are most common in the late afternoon and evening, they happen any time of the day or night. They move predominantly from the southwest to northeast, but can and do move in any direction. Their average forward speed is 30 mph, but that can vary from nearly stationary to more than 70 mph.

Tornado Alley
Tornado Alley is the nickname given to an area in the plains of the central U.S. that consistently experiences a high occurrence of tornado activity. Tornadoes in this region typically happen in late spring and occasionally the early fall. ("Dixie Alley" is another area along the Gulf Coast area that experiences a relatively high frequency of tornadoes during the late fall.)

The boundaries of Tornado Alley aren't clearly defined. Generally, the term refers to the region from extending from central Texas to northern Iowa, and from central Kansas and Nebraska to western Ohio. This region is ideally situated for violent, long-track tornadoes and the supercell storms that produce them.