Tornado climatology
The United States averaged 1,274 tornadoes per year in the last decade. April 2011 saw the most tornadoes ever recorded for any month in the US National Weather Service's history, 875; the previous record was 542 in one month. It has more tornadoes yearly than any other country and reports more violent (F4 and F5) tornadoes than anywhere else.
List of tornadoes causing 100 or more deaths
There is also meteorological uncertainty with the nature of many tornadoes on this list. Before the 1970s, and even now outside of North America, most tornado paths were not thoroughly surveyed to ensure that the storm was indeed a single tornado and not a series of tornadoes from the same storm (a tornado family). Often a single supercell can produce a new tornado soon after or even before the demise of an old tornado, giving the appearance to many observers that a single tornado has caused all the damage. On this list, if it is likely that the tornado was in fact two or more tornadoes, it will appear in "italics".