National Weather Service forecast offices issued life-saving tornado warnings with an average lead-time of 24 minutes. Warnings were in effect for more than 90 percent of the tornadoes.
To date, NOAA estimates the outbreak spawned 305 tornadoes, making this the largest tornado outbreak in history – surpassing the April 3-4, 1974 outbreak with 148 tornadoes. So far, the National Weather Service has surveyed damage from 178 tornadoes and determined that two topped the scale at EF-5, four were EF-4, and 21 were EF-3. Dozens more have been categorized as EF-2 or lower.
NOAA estimates there were more than 600 tornadoes during the month of April 2011, shattering previous records. The previous April tornado record was 267, set in 1974. The previous record number of tornadoes during any month was 542, set in May 2003. So far there have been an estimated 881 tornadoes in 2011. The annual tornado record is 1,817, set in 2004. May is historically the most active month for tornadoes.
With an estimated 327 deaths, this is the 3rd deadliest tornado outbreak on record, behind 1925 with 747 and 1932 with 332. So far, 2011 is the 13th deadliest year for tornadoes on record with 369. The deadliest year on record is 1925 with 794.