Tornadoes · United States · Iowa

Tornadoes in Grundy County, Iowa

42 tornadoes have crossed Grundy County since 1950, 2 of them surveyed so far this year and still preliminary, 36th of the 99 counties in Iowa with a tornado on record, an average of one every 1.8 years. They have killed 10 people and injured 78. 2 were rated F4 or EF4 and above, 1 at the top of the scale.

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
42
Deaths
10
Injuries
78
F4 and above
2
Worst on record
EF5, May 25, 2008

The deadliest in Grundy County

  1. EF5 Parkersburg–New Hartford tornado, IowaMay 25, 20089 killed, 70 injured
  2. F3, Grundy, Black Hawk and Buchanan counties, IowaApril 16, 19601 killed, 5 injured

The strongest

  1. EF5 Parkersburg–New Hartford tornado, IowaMay 25, 2008EF5, 41.0 mi (66 km)
  2. F4, Hardin and Grundy counties, IowaMay 30, 1989F4, 11.0 mi (18 km)
  3. F3, Grundy, Black Hawk and Buchanan counties, IowaApril 16, 1960F3, 29.8 mi (48 km)
  4. F2, Grundy and Hardin counties, IowaMarch 22, 1991F2, 20.0 mi (32 km)
  5. F2, Butler and Grundy counties, IowaJuly 2, 1999F2, 8.5 mi (14 km)
  6. F2, Grundy and Tama counties, IowaMay 10, 2001F2, 8.0 mi (13 km)
  7. F2, Grundy County, IowaOctober 14, 1966F2, 2.7 mi (4 km)
  8. F2, Grundy County, IowaApril 19, 1966F2, 2.3 mi (4 km)
  9. F2, Grundy County, IowaMay 10, 2001F2, 1.7 mi (3 km)

Every year with a tornado

The 23 years of the 76 in the record with a tornado in Grundy County. Each year links to every tornado in Iowa that year.

YearTornadoesDeathsInjuriesStrongest
20262EF1
20253Unrated
20232EF1
20162EF0
20144EF1
20093EF1
20082970EF5
20045F1
20021F0
20013F2
20001F0
19991F2
19911F2
19901F1
198913F4
19871F1
19781F1
19771F1
19751F1
19731F1
19712F1
19662F2
1960115F3

Every tornado that crossed Grundy County

42 tornadoes, newest first. The 2 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
July 20, 20263:56 PM CDTEF1Butler4.425
July 20, 20264:00 PM CDTUnratedGrundy2.00
August 18, 20257:25 AM CDTUnratedGrundy0.635
August 18, 20257:25 AM CDTUnratedGrundy4.550
August 18, 20257:16 AM CDTUnratedGrundy1.450
March 31, 20234:22 PM CDTEF1Grundy3.580$50,000
March 31, 20234:22 PM CDTEF1Grundy4.180$50,000
November 28, 20163:41 PM CSTEF0Grundy1.525
November 28, 20163:38 PM CSTEF0Grundy5.750$3,000
August 31, 20149:35 PM CDTEF0Grundy1.675
July 6, 20148:08 PM CDTEF0Grundy1.520
July 6, 20147:58 PM CDTEF1Grundy3.2100$200,000
June 29, 20148:18 PM CDTEF1Grundy1.950$30,000
June 21, 20097:25 PM CDTEF1Grundy2.170$10,000
June 21, 20097:20 PM CDTEF1Grundy2.390$25,000
June 21, 20096:51 PM CDTEF0Grundy0.430
May 25, 20085:07 PM CDTEF0Grundy1.150$1,000
May 25, 20084:48 PM CDTEF5Parkersburg–New Hartford tornado41.02,100970$100 million
May 21, 20043:22 PM CDTF0Grundy0.540
May 21, 20043:15 PM CDTF0Grundy0.540
May 21, 20042:49 PM CDTF0Grundy0.530
May 21, 20042:38 PM CDTF1Grundy3.5100$2,000
May 21, 20042:28 PM CDTF0Grundy3.050
April 18, 20026:30 PM CDTF0Grundy0.230$1,000
May 10, 20015:20 PM CDTF1Grundy1.0100$50,000
May 10, 20015:15 PM CDTF2Grundy8.0875$70,000
May 10, 20015:04 PM CDTF2Grundy1.7200$150,000
May 11, 20006:45 PM CDTF0Grundy0.330
July 2, 19999:45 PM CDTF2Butler8.550$100,000
March 22, 19915:25 PM CSTF2Grundy20.050$50,000 to $500,000
June 28, 19902:15 PM CDTF1Grundy5.530$500,000 to $5 million
May 30, 19897:50 PM CDTF4Hardin11.02003$500,000 to $5 million
July 14, 19878:00 PM CDTF1Grundy0.113$50 to $500
July 7, 19781:02 AM CDTF1Grundy1.060$5,000 to $50,000
July 6, 19776:00 PM CDTF1Grundy0.510$5,000 to $50,000
November 9, 19754:45 PM CSTF1Grundy0.1300$50,000 to $500,000
July 2, 19731:33 AM CDTF1Grundy30.310$5,000 to $50,000
May 31, 19717:20 PM CDTF1Grundy2.3200
May 31, 19717:20 PM CDTF1Grundy2.3200
October 14, 19666:30 PM GMT-5F2Grundy2.7100$500 to $5,000
April 19, 19666:00 PM GMT-6F2Grundy2.3200$5,000 to $50,000
April 16, 19602:30 PM GMT-6F3Grundy29.880015$50,000 to $500,000

Nearby

Warnings in force in Grundy CountyThe forecast for Grundy CountyThe live radar over Grundy 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.