Tornadoes and Hail in Iowa, May 18, 1971

Name: Tornadoes and Hail in Iowa, May 18, 1971
Start: 1971-05-18T00:15
End: 1971-05-18T21:55
Location: Iowa

May 18, 1971 · 24 events in 11 counties and zones

11 thunderstorm wind, 7 tornado, 6 hail, as filed by the National Weather Service.

Where it happened

Every event with a place to put it. Tap one for its entry below.

Tornadoes
Tropical storms and surge
Floods
Wind
Hail
Winter weather
Heat and drought
Cold
Fire, smoke and dust
Marine and coastal
Other

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The toll

Deaths: 0
Injuries: 0
Property damage: $625,000
Crop damage: None recorded
Events: 24

Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.

Event by event

11 thunderstorm wind, 7 tornado, 6 hail. Local standard time, as filed.

Hail, Boone

When: May 18, 12:15 AM CST
Where: Boone County
Measured: 1 in hail
Coordinates: 41.880, -93.680

Thunderstorm Wind, Marion

When: May 18, 1:50 PM CST
Where: Marion County
Coordinates: 41.380, -92.900

Tornado, Mahaska

When: May 18, 2:00 PM CST
Where: Mahaska County
Rating: F0
Path width: 33 yd
Property damage: $250,000
Coordinates: 41.450, -92.800

Tornado, Marion

When: May 18, 2:15 PM CST
Where: Marion County
Rating: F1
Path width: 33 yd
Property damage: $25,000
Coordinates: 41.330, -93.100

Thunderstorm Wind, Benton

When: May 18, 2:45 PM CST
Where: Benton County
Coordinates: 41.880, -92.280

Thunderstorm Wind, Benton

When: May 18, 3:01 PM CST
Where: Benton County
Coordinates: 42.000, -92.000

Tornado, Benton

When: May 18, 3:08 PM CST
Where: Benton County
Rating: F3
Path length: 4.3 mi
Path width: 300 yd
Property damage: $25,000
Coordinates: 41.900, -92.080

Hail, Benton

When: May 18, 3:10 PM CST
Where: Benton County
Measured: 2 in hail
Coordinates: 41.880, -92.080

Tornado, Benton

When: May 18, 3:12 PM CST
Where: Benton County
Rating: F3
Path length: 4.3 mi
Path width: 200 yd
Property damage: $250,000
Coordinates: 42.000, -91.870

Tornado, Keokuk

When: May 18, 4:00 PM CST
Where: Keokuk County
Rating: F1
Path width: 33 yd
Property damage: $25,000
Coordinates: 41.330, -92.300

Thunderstorm Wind, Dubuque

When: May 18, 4:15 PM CST
Where: Dubuque County
Coordinates: 42.380, -90.900

Thunderstorm Wind, Dubuque

When: May 18, 4:30 PM CST
Where: Dubuque County
Coordinates: 42.500, -90.680

Thunderstorm Wind, Appanoose

When: May 18, 4:30 PM CST
Where: Appanoose County
Coordinates: 40.700, -93.080

Hail, Appanoose

When: May 18, 4:50 PM CST
Where: Appanoose County
Measured: 3 in hail
Coordinates: 40.700, -93.000

Thunderstorm Wind, Appanoose

When: May 18, 5:10 PM CST
Where: Appanoose County
Coordinates: 40.880, -92.780

Hail, Wapello

When: May 18, 5:20 PM CST
Where: Wapello County
Measured: 2.5 in hail
Coordinates: 41.000, -92.580

Thunderstorm Wind, Wapello

When: May 18, 5:20 PM CST
Where: Wapello County
Coordinates: 41.000, -92.580

Tornado, Wapello

When: May 18, 5:23 PM CST
Where: Wapello County
Rating: F1
Path width: 33 yd
Property damage: $25,000
Coordinates: 41.030, -92.600

Tornado, Iowa

When: May 18, 5:45 PM CST
Where: Iowa County
Rating: F1
Path length: 5.1 mi
Path width: 100 yd
Property damage: $25,000
Coordinates: 41.780, -92.050

Hail, Johnson

When: May 18, 6:50 PM CST
Where: Johnson County
Measured: 2 in hail
Coordinates: 41.700, -91.500

Hail, Linn

When: May 18, 7:15 PM CST
Where: Linn County
Measured: 0.75 in hail
Coordinates: 41.880, -91.400

Thunderstorm Wind, Keokuk

When: May 18, 8:00 PM CST
Where: Keokuk County
Coordinates: 41.200, -92.280

Thunderstorm Wind, Johnson

When: May 18, 9:00 PM CST
Where: Johnson County
Coordinates: 41.700, -91.500

Thunderstorm Wind, Dubuque

When: May 18, 9:55 PM CST
Where: Dubuque County
Coordinates: 42.280, -90.780

What these are

Hail: Hail three-quarters of an inch or larger, or smaller hail that caused damage, filed with the largest stone measured.
Thunderstorm Wind: Winds from a thunderstorm of 50 knots (58 mph) or more, or lower winds that caused damage or casualties. Measured gusts are marked MG, estimated EG.
Tornado: A violently rotating column of air in contact with the ground and extending from a thunderstorm, filed with its path, width and Fujita or Enhanced Fujita rating from the damage survey.

After NWS Directive 10-1605, the rules offices file Storm Data by.

The same day elsewhere

Every storm in Iowa in 1971 Every state in 1971 This day in weather history The tornado archive for Iowa, 1971

Sources

NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 10011355, 10011356, 10011357, 10011358, 10011359, 10011360, 10011361, 10011362, 10011363, 10011364, 10011365, 10011366, 10011367, 10011368, 10011369, 10011370, 10011371, 10011372, 10011373, 10011374, 10011375, 10012157, 10012158, 10012159.