Tornadoes · United States · Iowa · 1959
F4 tornado, Wayne County, Iowa, May 20, 1959
This F4 tornado ran 17.2 miles across Wayne County on May 20, 1959, touching down at 8:00 PM GMT-5 and reaching 440 yards wide. It killed nobody and injured 5, and did $50,000 to $500,000 of property damage.
The rating scale
Tracks are drawn in the color of the rating. The Fujita scale rates the damage rather than measuring the wind: the speeds are what that damage is taken to imply.
F040 to 72 mph
Light damage. Surface peeled off some roofs, gutters and siding damaged, branches broken, shallow-rooted trees pushed over.
F173 to 112 mph
Moderate damage. Roofs badly stripped, mobile homes overturned or badly damaged, exterior doors lost, windows broken.
F2113 to 157 mph
Considerable damage. Roofs torn off well-built houses, frame homes shifted on their foundations, mobile homes destroyed, large trees snapped or uprooted, cars lifted off the ground.
F3158 to 206 mph
Severe damage. Whole stories of well-built houses destroyed, large buildings badly damaged, trains overturned, trees debarked, heavy cars lifted and thrown.
F4207 to 260 mphthis tornado
Devastating damage. Well-built houses leveled, structures with weak foundations moved some distance, cars thrown and large missiles generated.
F5261 to 318 mph
Incredible damage. Strong frame houses swept off their foundations, car-sized missiles thrown more than 100 meters, steel-reinforced concrete badly damaged, high-rise buildings deformed.
Unrated
The survey recorded a tornado but could not put a number on it, most often because it crossed open country and damaged nothing a rating can be read from.
The record
- Rating
- F4
- Date
- May 20, 1959
- Touchdown
- 8:00 PM GMT-5 (01:00 UTC)
- Path length
- 17.2 miles (27.7 km)
- Path width
- 440 yards (402 m)
- Deaths
- 0
- Injuries
- 5
- Property damage
- $50,000 to $500,000
- County
- Wayne County
- Touchdown point
- 40.700, -93.150
- Lift-off point
- 40.870, -92.900
- Record number
- 256
The surface observations
Ottumwa (OTM), 60 km from the path, in the two hours either side.
| Time (UTC) | Temp (°F) | Dew point (°F) | Wind | Gust (kt) | Pressure (mb) | Weather |
|---|---|---|---|---|---|---|
| 23:00 UTC | 73 | 64 | 90° 15 kt | |||
| 00:00 UTC | 71 | 63 | 113° 15 kt | TS SHRA | ||
| 01:00 UTC | 71.6 | 62 | 113° 18 kt | |||
| 02:00 UTC | 72 | 63 | 135° 19 kt | TS |
From the Iowa Environmental Mesonet's archive of airport observations.
This ground now
The live radar over the trackEvery 1959 tornado in IowaEvery tornado in Iowa since 1950Warnings in force in Iowa nowThe forecast where you are
The other tornadoes of May 20, 1959
12 more were confirmed in the United States that day.
| Date | Time | Rating | Where | Path (mi) | Width (yd) | Deaths | Injuries | Damage |
|---|---|---|---|---|---|---|---|---|
| May 20 | 5:00 PM GMT-5 | F0 | Meade, KS | 0.1 | 10 | |||
| May 20 | 6:00 PM GMT-5 | F1 | Callahan, TX | 0.2 | 13 | $50 to $500 | ||
| May 20 | 8:00 PM GMT-5 | F1 | Dodge, NE | 0.1 | 10 | $5,000 to $50,000 | ||
| May 20 | 8:00 PM GMT-5 | F1 | Jefferson, NE | 40.6 | 10 | $5,000 to $50,000 | ||
| May 20 | 8:51 PM GMT-5 | F0 | Marion, KS | 0.1 | 10 | |||
| May 20 | 8:58 PM GMT-5 | F0 | Marion, KS | 0.1 | 10 | |||
| May 20 | 9:00 PM GMT-5 | F2 | Smith, KS | 0.1 | 10 | |||
| May 20 | 9:30 PM GMT-5 | F1 | Dallas, AL | 0.1 | 200 | $50 to $500 | ||
| May 20 | 10:00 PM GMT-5 | F2 | Saunders, NE | 12.0 | 10 | $5,000 to $50,000 | ||
| May 20 | 10:00 PM GMT-5 | F1 | Dodge, NE | 0.3 | 100 | $5,000 to $50,000 | ||
| May 20 | 11:00 PM GMT-5 | F1 | Andrew, MO | 0.2 | 17 | $5,000 to $50,000 | ||
| May 20 | 12:30 AM GMT-5 | F1 | Mercer, MO | 5.9 | 10 | $5,000 to $50,000 |
What this means
Ratings are the survey's, read off the damage rather than measured; the rating scale is above. Tornado counts rise through the record as reporting improved, so a year in the 1950s is not comparable with one today except for the strongest tornadoes, which were always noticed.
Sources
NOAA Storm Prediction Center tornado database, 1950-2025, the official record kept by NOAA's Storm Prediction Center.