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Tornado History

Delaware Tornado History

This county-level tornado history page focuses on Delaware, Iowa. The records below identify 37 tornadoes from 1960 through 2025, including a highest listed rating of F4 (Devastating damage). NOAA damage estimates in this group total at least $29.9M, with 0 deaths and 18 injuries recorded across the listed events.

Key Tornado Statistics

Total Tornadoes37
Total Deaths0
Total Injuries18
Property Damage$29.9M
Avg Length4.9 mi
Avg Width98 yd

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Key Tornado Facts for Delaware, Iowa

Top local patterns from the historical tornado records in this group.

Average 0.6 tornadoes per year (1.0/yr in last decade)
May is the peak tornado month with 9 recorded events
Deadliest tornado: F2 in Delaware, Iowa with 0 deaths
1991 was the most active year with 5 tornadoes
The 1990s had the most tornado activity (7 events)
Longest tornado: 17 miles in Delaware, Iowa
Widest tornado: 880.0 yards in Delaware, Iowa
Most tornadoes in one day: 3 on Jul 14, 2021

Monthly Distribution

Shows tornado frequency across months of the year, highlighting seasonal patterns and peak tornado periods.

January
February
March
April
May
June
July
August
September
October
November
December

Summary: In Delaware, Iowa, May is the most active month with 9 tornadoes.

Annual Tornado Trend

Shows year-by-year tornado counts, making active years and quiet stretches easier to spot.

5420

Summary: 1991 was the most active year with 5 recorded tornadoes.

Tornado Intensity Distribution

Shows the breakdown of tornadoes by EF/F rating.

F0
EF0
F1
EF1
F2
EF2
F4
Unknown
EFU

Summary: EF1 tornadoes are the most common in this group, with 12 recorded events.

Property Damage Trends

Visualizes reported property damage over time. Bars use a log-like scale so very large damage years do not flatten the rest of the chart.

$25.2M$2.5M$252K$0

Summary: The highest reported property damage year in this group is 1990 with at least $25.2M in NOAA-listed property damage.

Historical Track Sketch

F4 March 13, 19901990F4 August 12, 19741974F2 November 15, 19601960F2 May 4, 19641964F2 November 15, 19881988F2 June 2, 19901990F2 March 22, 19911991EF2 June 28, 20172017EF1 April 26, 20092009EF1 March 31, 20072007EF1 May 25, 20082008EF1 May 25, 20082008EF1 June 16, 20142014F1 August 26, 20042004EF1 June 19, 2014F1 August 7, 1986F1 May 14, 1991EF1 July 23, 2016EF1 July 23, 2016EF1 July 14, 2021EF1 July 14, 2021EF1 March 31, 2023EF1 March 31, 2023F0 May 8, 1988F0 May 8, 1988F0 May 14, 1991F0 March 22, 1991F0 April 8, 1991F0 June 15, 1966F0 August 14, 1985F0 August 24, 1985F0 June 1, 2001F0 May 10, 2001EF0 July 11, 2025Unknown May 16, 1977EFU June 9, 2019EFU July 14, 2021© OpenStreetMap contributors

Notable Tornado Records

The table highlights the strongest and most damaging records in this page's local dataset. Damage totals are NOAA-reported minimum estimates where available.

DateRatingAreaLengthWidthDeathsInjuriesMin. property damage
March 13, 1990F4Delaware, Iowa9 mi200 yd00$25.0M
August 12, 1974F4Delaware, Iowa5 mi400 yd012$2.5M
November 15, 1960F2Delaware, Iowa10.5 mi70 yd00$250K
May 4, 1964F2Delaware, Iowa4.7 mi200 yd02$250K
November 15, 1988F2Delaware, Iowa11 mi63 yd00$250K
June 2, 1990F2Delaware, Iowa5 mi67 yd00$250K
March 22, 1991F2Delaware, Iowa17 mi80 yd01$250K
June 28, 2017EF2Delaware, Iowa1.22 mi30 yd00N/A
April 26, 2009EF1Delaware, Iowa6.06 mi100 yd00$500K
March 31, 2007EF1Delaware, Iowa7.85 mi200 yd00$162K
May 25, 2008EF1Delaware, Iowa11.07 mi880 yd00$100K
May 25, 2008EF1Delaware, Iowa6.95 mi250 yd00$100K

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Source And Limits

Data source: NOAA/NCEI. TornadoTrace summarizes historical records for screening and research. Coordinates, damage estimates, narratives, and event details can be approximate, incomplete, revised, or missing. Do not use this page as legal, insurance, engineering, real estate, emergency management, or safety advice.