The Biggest Tornado Outbreaks in US History
The biggest US tornado outbreaks by count: April 27, 2011 (216 tornadoes), April 3-4, 1974 (148), April 11, 1965 (47), and more.
Ranked by Tornado Count
| Rank | Date | Tornadoes | Deaths |
|---|---|---|---|
| 1 | April 25-28, 2011 | 360 (4-day sequence) | 324 |
| 2 | April 27, 2011 (single day) | 216 | 316 |
| 3 | April 3-4, 1974 | 148 | 335 |
| 4 | May 4-5, 2007 | ~90 | 13 |
| 5 | February 5-6, 2008 | 87 | 57 |
| 6 | May 22-24, 2011 | ~85 | 178 |
| 7 | April 14-16, 2011 | ~78 | 39 |
| 8 | March 12-14, 2020 | ~65 | 25 |
| 9 | April 11, 1965 (Palm Sunday) | 47 | 271 |
| 10 | December 10, 2021 (Quad-State) | ~40 | 89 |
Historic Outbreaks in Detail
2011 Super Outbreak (April 25-28)
The largest tornado outbreak in recorded history. 360 confirmed tornadoes across 21 US states over 4 days. April 27 alone produced 216 tornadoes - a single-day record. Full story →
1974 Super Outbreak (April 3-4)
Until 2011, the largest US tornado outbreak. 148 confirmed tornadoes across 13 US states in 24 hours. Six F5 tornadoes touched down. Xenia, OH was the signature event. Full story →
Palm Sunday 1965 (April 11)
47 tornadoes across 6 US states in a single afternoon. 17 F4 tornadoes touched down. 271 killed. Full story →
May 3-4, 1999 Oklahoma Outbreak
66 tornadoes across Oklahoma and Kansas. The Bridge Creek-Moore F5 produced the highest wind speed ever measured (301 mph). Full story →
Super Tuesday 2008 (February 5-6)
Unusual mid-winter outbreak that produced 87 tornadoes and 57 deaths across the Southeast. Union University in Jackson, TN was heavily damaged.
Quad-State Outbreak (December 10, 2021)
Rare late-fall outbreak that killed 89 people. The Mayfield, KY EF4 traveled 165 miles - one of the longest tornado paths on record for December.
Ranked by Deaths
| Rank | Date | Deaths |
|---|---|---|
| 1 | April 3-4, 1974 | 335 |
| 2 | April 25-28, 2011 | 324 |
| 3 | April 5-6, 1936 | ~500 (Tupelo + Gainesville) |
| 4 | April 24, 1908 | ~324 |
| 5 | April 11, 1965 (Palm Sunday) | 271 |
| 6 | February 21, 1971 | 121 |
| 7 | April 11-12, 2020 Easter Sunday | 34 |
| 8 | December 10, 2021 (Quad-State) | 89 |
Anatomy of a Major Outbreak
Every major outbreak shares similar atmospheric ingredients:
- Deep low-pressure system at the surface
- Strong upper-level jet streak providing wind shear
- Warm moist air at the surface (dew points 65°F+)
- Cold dry air aloft
- Dryline or cold front as the trigger
- Sustained atmospheric instability over a large area
When these ingredients align over a wide area for many hours, dozens of supercells develop simultaneously - producing outbreak-scale tornado events.
Detection and Warning Improvements
Modern outbreaks are detected and warned days in advance:
- SPC issues Enhanced/Moderate/High Risk outlooks 24-72 hours ahead
- PDS Tornado Watches issued 4-6 hours before peak events
- Individual Tornado Warnings issued 10-30 minutes ahead of tornadoes
This is why modern outbreaks kill far fewer people than 1974 or 1936 events, despite similar tornado counts.
The Future of Outbreaks
Research suggests that the frequency of major outbreaks may be increasing, especially in the Southeast. As tornado activity shifts east (Tornado Alley 2.0), outbreak-heavy geography is moving into more populated regions.
Try the interactive simulator
Place an EF0–EF5 tornado anywhere in the world and see modeled fatalities, structural damage, and economic loss based on real census data.
Launch simulator →Try the interactive simulator
Place an EF0–EF5 tornado anywhere in the world and see modeled fatalities, structural damage, and economic loss based on real census data.
Launch simulator →