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 tropical cyclone-spawned tornadoes
These are the tropical cyclones that are known to have spawned tornadoes. The list is most complete for the U.S., but does include other areas. Within the United States 1,163 tornadoes were associated with tropical cyclones, accounting for slightly under 6% of all tornadoes. The most tornadoes spawned by a single tropical cyclone were associated with Hurricane Ivan, which spawned 120 tornadoes.