Top 10 Killer Tornadoes

Tornadoes kill dozens and sometimes hundreds of people every year in the United States. Warning systems have improved dramatically, however, so some of the deadliest tornadoes were recorded many decades ago. In some cases, a single tornado caused hundreds of deaths. Following are the 10 deadliest on record, based on data from the Federal Emergency Management Agency (FEMA). Strengths are measured from F1 to F5 (strongest) on the Fujita scale.