Tornadoes · United States · Iowa

Tornadoes in Delaware County, Iowa

49 tornadoes have crossed Delaware County since 1950, 4 of them surveyed so far this year and still preliminary, 18th of the 99 counties in Iowa with a tornado on record, an average of one every 1.6 years. They have killed 0 people and injured 26. 3 were rated F4 or EF4 and above.

The rating scale

Tracks are drawn in the color of the rating. The United States rated tornadoes on Ted Fujita’s F scale until 31 January 2007 and on the Enhanced Fujita scale after it. Both run from 0 to 5, and both rate the damage rather than measure the wind: the speeds are what that damage is taken to imply.

  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.

Now

Tornadoes
49
Deaths
0
Injuries
26
F4 and above
3
Worst on record
F4, March 13, 1990

The strongest

  1. F4, Linn, Delaware, Clayton and Allamakee counties, IowaApril 30, 1954F4, 80.4 mi (129 km)
  2. F4, Linn, Delaware, Jones and Dubuque counties, IowaMarch 13, 1990F4, 19.0 mi (31 km)
  3. F4, Delaware County, IowaAugust 12, 1974F4, 5.0 mi (8 km)
  4. EF3, Buchanan and Delaware counties, IowaMay 25, 2008EF3, 32.0 mi (51 km)
  5. F3, Buchanan and Delaware counties, IowaJuly 27, 1995F3, 20.0 mi (32 km)
  6. F3, Delaware County, IowaJune 19, 1993F3, 9.0 mi (14 km)
  7. F3, Delaware County, IowaJuly 12, 1971F3, 0.1 mi (0 km)
  8. F2, Iowa, Benton, Linn and Delaware counties, IowaApril 30, 1954F2, 65.8 mi (106 km)
  9. F2, Linn, Delaware, Jones and Dubuque counties, IowaSeptember 28, 1972F2, 64.5 mi (104 km)
  10. F2, Delaware County, IowaJune 26, 1969F2, 26.9 mi (43 km)

Every year with a tornado

The 29 years of the 76 in the record with a tornado in Delaware County. Each year links to every tornado in Iowa that year.

YearTornadoesDeathsInjuriesStrongest
20264EF1
20251EF0
20232EF1
20213EF1
20191Unrated
20171EF2
20162EF1
20142EF1
20091EF1
200823EF3
20071EF1
20041F1
20012F0
19951F3
19931F3
199151F2
19902F4
19883F2
198613F1
19852F0
19771F0
1974112F4
197213F2
197112F3
19691F2
19661F0
196412F2
19601F2
19543F4

Every tornado that crossed Delaware County

49 tornadoes, newest first. The 4 at the top are this year's, from the surveying office rather than SPC's published database, and their ratings are marked as preliminary.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
April 14, 20265:25 PM CDTEF1Buchanan4.350
August 11, 20267:31 AM CDTEF1Delaware2.4150
August 11, 20267:44 AM CDTEF1Delaware1.5100
August 11, 20267:45 AM CDTEF1Delaware2.675
July 11, 20254:17 PM CDTEF0Delaware1.740
March 31, 20235:32 PM CDTEF1Delaware11.190
March 31, 20235:20 PM CDTEF1Delaware4.150
July 14, 20219:40 PM CDTUnratedDelaware0.410
July 14, 20217:54 PM CDTEF1Delaware1.130
July 14, 20217:50 PM CDTEF1Delaware1.440
June 9, 20193:53 PM CDTUnratedBuchanan7.310
June 28, 20177:14 PM CDTEF2Jones2.530
July 23, 20164:18 PM CDTEF1Delaware0.210
July 23, 20164:06 PM CDTEF1Delaware0.125$5,000
June 19, 20143:04 PM CDTEF1Delaware15.775$50,000
June 16, 20149:33 PM CDTEF1Delaware12.650$100,000
April 26, 20094:52 PM CDTEF1Linn21.0100$1.0 million
May 25, 20087:31 PM CDTEF1Delaware8.5250$350,000
May 25, 20086:05 PM CDTEF3Buchanan32.01,2323$1.1 million
March 31, 20075:29 PM CDTEF1Delaware11.8200$202,000
August 26, 200410:51 PM CDTF1Delaware4.2440$70,000
June 1, 20015:12 PM CDTF0Delaware0.110
May 10, 20015:38 PM CDTF0Delaware0.110
July 27, 19953:50 PM CDTF3Buchanan20.0150$500,000 to $5 million
June 19, 19933:56 PM CDTF3Delaware9.0200$5,000 to $50,000
May 14, 19911:35 PM CDTF1Delaware17.050$5,000 to $50,000
May 14, 19911:31 PM CDTF0Delaware0.117$500 to $5,000
April 8, 19913:30 PM CDTF0Delaware0.517$50 to $500
March 22, 19918:00 PM CSTF0Delaware0.120$500 to $5,000
March 22, 19917:25 PM CSTF2Delaware17.0801$50,000 to $500,000
June 2, 199012:43 PM CDTF2Buchanan10.567$50,000 to $500,000
March 13, 19904:53 PM CSTF4Linn19.0200$5 million to $50 million
November 15, 19889:05 PM CSTF2Delaware11.063$50,000 to $500,000
May 8, 19883:22 PM CDTF0Delaware0.520$5,000 to $50,000
May 8, 19883:15 PM CDTF0Delaware0.520$5,000 to $50,000
August 7, 19866:45 PM CDTF1Delaware0.1233$5,000 to $50,000
August 24, 198512:15 PM CDTF0Delaware1.013
August 14, 19851:15 PM CDTF0Delaware0.110
May 16, 19774:00 PM CDTF0Delaware0.110
August 12, 19745:20 PM CDTF4Delaware5.040012$500,000 to $5 million
September 28, 19722:50 PM CDTF2Linn64.52,2003$500,000 to $5 million
July 12, 197110:10 PM CDTF3Delaware0.18332$500,000 to $5 million
June 26, 19699:30 PM GMT-5F2Delaware26.9300$50,000 to $500,000
June 15, 19665:30 PM GMT-5F0Delaware0.110under $50
May 4, 19647:15 PM GMT-5F2Delaware4.72002$50,000 to $500,000
November 15, 19603:20 PM GMT-6F2Delaware10.570$50,000 to $500,000
April 30, 19548:05 PM GMT-5F2Jones16.650
April 30, 19548:00 PM GMT-5F2Iowa65.8200
April 30, 19548:00 PM GMT-5F4Linn80.4200

Nearby

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

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.