FACTBOX-Deadliest tornadoes of last 25 years in the United States

A pair of tornadoes killed at least 23 people on Sunday in Alabama, causing infrastructure damage with at least 150 miles per hour (241 kph) winds in the deadliest twister to hit the United States in almost six years.

The following is a list of some of the deadliest single tornadoes and tornado outbreaks in the United States over the last quarter century: * A so-called Super Outbreak of 362 tornadoes hit the southeastern United States over three days in April 2011, killing an estimated 321 people, according to the National Oceanic and Atmospheric Administration (NOAA). Three of the tornadoes were rated EF-5, the top of the five-step Enhanced Fujita scale that meteorologists use to measure tornado strength. The system struck Alabama the hardest, wrecking Tuscaloosa and Birmingham and causing about $11 billion in damages across 12 states.

* The deadliest tornado to hit the United States in the last several decades struck Joplin, Missouri on May 22, 2011 and killed at least 158 people, NOAA said. Damage from the storm exceeded $3 billion, the most of any single tornado in U.S. history. * The so-called Super Tuesday Outbreak of 87 tornadoes in the southeastern United States on Feb. 5, 2008, killed 57 people, according to NOAA. It had the longest footprint of any tornado in U.S. history, according to private forecaster Accuweather, touching down continuously for 122 miles (196 km) through Arkansas.

* A tornado outbreak in the Oklahoma City, Oklahoma, metropolitan area on May 3, 1999, spawned 61 tornadoes and killed 55 people, with one single tornado responsible for 36 deaths, according to the Weather Channel. * An outbreak of seven tornadoes in central Florida in February 1998 killed 42 people and injured 260 others in the state's deadliest tornado outbreak since 1962, the National Weather Service reported.

* In April 2014, an outbreak of dozens of tornadoes stirred up by a powerful storm system hit the Southeast and Midwest over a three-day period and killed 32 people in Iowa, Oklahoma, Arkansas, Mississippi, Alabama and Tennessee, according to NOAA. * A tornado killed 24 people on May 20, 2013 in Moore, Oklahoma. The tornado had winds over 200 miles per hour (322 kph), giving it the most severe rating of EF-5. It lasted about 40 minutes, and caused billions of dollars worth of damage, according to NOAA. (Compiled by Gabriella Borter in New York; Editing by Scott Malone and Grant McCool)

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