Tornadoes in Story County, Iowa

1. F0 / EF040 to 72 mph on the F scale, 65 to 85 mph on the EF scale

   Light damage. Surface peeled off some roofs, gutters and siding damaged, branches broken, shallow-rooted trees pushed over.

2. F1 / EF173 to 112 mph on the F scale, 86 to 110 mph on the EF scale

   Moderate damage. Roofs badly stripped, mobile homes overturned or badly damaged, exterior doors lost, windows broken.

3. F2 / EF2113 to 157 mph on the F scale, 111 to 135 mph on the EF scale

   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.

4. F3 / EF3158 to 206 mph on the F scale, 136 to 165 mph on the EF scale

   Severe damage. Whole stories of well-built houses destroyed, large buildings badly damaged, trains overturned, trees debarked, heavy cars lifted and thrown.

5. F4 / EF4207 to 260 mph on the F scale, 166 to 200 mph on the EF scale

   Devastating damage. Well-built houses leveled, structures with weak foundations moved some distance, cars thrown and large missiles generated.

6. F5 / EF5261 to 318 mph on the F scale, over 200 mph on the EF scale

   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.

7. 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.

Tornadoes

66

Deaths

1

Injuries

47

F4 and above

2

Worst on record

F5, June 13, 1976

1. F3, Story, Hardin, Butler and Chickasaw counties, IowaMay 20, 19531 killed

1. F5 Jordan tornado, IowaJune 13, 1976F5, 21.3 mi (34 km)
2. F4, Hamilton, Story, Hardin and Marshall counties, IowaMay 24, 1989F4, 66.0 mi (106 km)
3. F3, Story, Hardin, Butler and Chickasaw counties, IowaMay 20, 1953F3, 116.1 mi (187 km)
4. F3, Story and Hardin counties, IowaMarch 22, 1991F3, 43.0 mi (69 km)
5. F3, Story County, IowaMarch 13, 1990F3, 9.0 mi (14 km)
6. F3, Story County, IowaJune 15, 1950F3, 5.6 mi (9 km)
7. EF2, Polk and Story counties, IowaMay 21, 2024EF2, 40.8 mi (66 km)
8. F2, Story County, IowaMay 31, 1959F2, 17.0 mi (27 km)
9. F2, Polk and Story counties, IowaMarch 13, 1990F2, 15.0 mi (24 km)
10. F2, Story County, IowaJune 8, 1967F2, 14.4 mi (23 km)

Before 1950 the record is Thomas P. Grazulis’s list of significant tornadoes: those rated F2 or stronger, and weaker ones that killed somebody. 11 of them crossed Story County, killing 80. They are not in the figures above, which are SPC's from 1950.

Significant tornadoes only

Grazulis listed tornadoes rated F2 or stronger, and weaker ones that killed somebody. Most tornadoes are weaker than F2, so the list holds a fraction of the tornadoes that happened.

The early years are thin

A tornado is on record only where somebody saw it and wrote it down. The count rises through the 1800s with settlement and newspapers, not with the weather.

Rated from accounts

Grazulis rated each tornado decades later from newspaper reports, Weather Bureau records and local histories, not from a damage survey.

The tracks are reconstructed

Tornado Archive drew each path through the places Grazulis names, most often as a straight line from the first to the last. A track can miss a town it hit, and a tornado with one named place is a point. The counties are today’s.

A separate record

SPC’s database, from 1950, counts every confirmed tornado of any strength. The two are kept apart on every page and never added together.

Warnings in force in Story CountyThe forecast for Story CountyThe live radar over Story CountyEvery county in Iowa

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.

NOAA Storm Prediction Center tornado database, 1950-2025, the official record kept by NOAA's Storm Prediction Center. Before 1950: Thomas P. Grazulis, Significant Tornadoes 1680-1991 and Significant Tornadoes 1880-1989, as digitized by Tornado Archive (Maas and others, 2024). Public domain. Counties assigned by this site from today’s NWS county lines.