| Type | Tornado outbreak, Flood event |
|---|---|
| Duration | May 3, 2003–May 11, 2003 |
| Highest winds |
|
| Tornadoes confirmed | 363 tornadoes (62 significant)[note 1] |
| Max. rating1 | F4 tornado |
| Duration of tornado outbreak2 | 7 days, 22 hours |
| Largest hail | 4.75 in (12.1 cm) in Mahaska County, Iowa |
| Fatalities | 42 deaths (+9 non-tornadic deaths), 652 injuries (+52 non-tornadic injuries) |
| Damage | US$4.1 billion (US$5.8 billion 2019 CPI) |
| Areas affected | Great Plains, Eastern United States |
| 1Most severe tornado damage; see Fujita scale 2Time from first tornado to last tornado Part of the Tornadoes of 2003 | |
From May 3 to May 11, 2003, a prolonged and destructive series of tornado outbreaks affected much of the Great Plains and Eastern United States. Most of the severe activity was concentrated between May 4 and May 10, which saw more tornadoes than any other week-long span in recorded history; 335 tornadoes occurred during this period, concentrated in the Ozarks and central Mississippi River Valley. Additional tornadoes were produced by the same storm systems from May 3 to May 11, producing 363 tornadoes overall, of which 62 were significant.[note 1] Six of the tornadoes were rated F4, and of these four occurred on May 4, the most prolific day of the tornado outbreak sequence; these were the outbreak's strongest tornadoes. Damage caused by the severe weather and associated flooding amounted to US$4.1 billion (US$5.8 billion in 2016), making it the costliest U.S. tornado outbreak of the 2000s. A total of 50 deaths and 713 injuries were caused by the severe weather, with a majority caused by tornadoes; the deadliest tornado was an F4 that struck Madison and Henderson counties in Tennessee, killing 11. In 2023, tornado expert Thomas P. Grazulis created the outbreak intensity score (OIS) as a way to rank various tornado outbreaks. The tornado outbreak sequence of May 2003 received an OIS of 232, making it the fourth worst tornado outbreak in recorded history.[2]
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