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Tornado in Delaware County, Iowa
40 tornadoes events in the NCEI Storm Events record, 1950 to 2026. Event types counted: Tornado.
NCEI notes that Storm Data is compiled from a variety of sources including the National Weather Service, other federal, state and local agencies, the media and the public; that property and crop damage figures are estimates; and that some events are recorded by NWS forecast zone rather than by county. FEMA notes that NFIP claim records are redacted and aggregated to protect the privacy of policyholders. Storm records through 30 Jun 2026.
Delaware County, Iowa, has 40 tornado events in the NCEI record since 1950, with at least one in 25 different years.
May is the busiest month, with 9 of the recorded events. The last 20 years account for 17 events against 13 in the 20 years before, a change that reflects reporting practice as much as weather.
The county holds 1.1% of the 3,501 tornado events recorded in Iowa; its 6.9 per 100 square miles compares with 6.3 statewide.
By rating: 11 at (E)F0, 16 at (E)F1, 7 at (E)F2, 1 at (E)F3, 2 at (E)F4, 0 at (E)F5 and 3 unrated. Tornadoes before 2007 carry the original Fujita rating.
Compared with Iowa
| Measure | Delaware County | Iowa | US |
|---|---|---|---|
| Tornado events since 1950 | 40 | 3,501 | 81,281 |
| Per 100 square miles | 6.9 | 6.3 | 2.3 |
| Per 10,000 residents | 22.8 | 11.0 | 2.4 |
| Deaths recorded | 0 | 100 | 6,410 |
| Busiest month | May | May | May |
By year
Seasonality
0Feb
0Mar
6Apr
3May
9Jun
8Jul
7Aug
5Sep
0Oct
0Nov
2Dec
0
Magnitude distribution
Enhanced Fujita scale wind estimates
- EF0/F0
- 65–85 mph (EF0)
- EF1/F1
- 86–110 mph (EF1)
- EF2/F2
- 111–135 mph (EF2)
- EF3/F3
- 136–165 mph (EF3)
- EF4/F4
- 166–200 mph (EF4)
- EF5/F5
- over 200 mph (EF5)
- Unrated
- no rating recorded
Tornado rating as recorded (Fujita scale before February 2007, Enhanced Fujita after).
Recorded events
All 40 events, most recent first. Magnitude is hail size, tornado rating or wind speed as recorded.
| Date | Event type | Magnitude | Property damage | Crop damage | Deaths | Injuries | Geography |
|---|---|---|---|---|---|---|---|
| 14 Apr 2026 | Tornado | EF1 | — | — | — | — | County |
| 11 Jul 2025 | Tornado | EF0 | — | — | — | — | County |
| 31 Mar 2023 | Tornado | EF1 | — | — | — | — | County |
| 31 Mar 2023 | Tornado | EF1 | — | — | — | — | County |
| 14 Jul 2021 | Tornado | EF1 | — | — | — | — | County |
| 14 Jul 2021 | Tornado | EF1 | — | — | — | — | County |
| 14 Jul 2021 | Tornado | EF unrated | — | — | — | — | County |
| 9 Jun 2019 | Tornado | EF unrated | — | — | — | — | County |
| 28 Jun 2017 | Tornado | EF2 | — | — | — | — | County |
| 23 Jul 2016 | Tornado | EF1 | $5K | — | — | — | County |
| 23 Jul 2016 | Tornado | EF1 | — | — | — | — | County |
| 19 Jun 2014 | Tornado | EF1 | $50K | — | — | — | County |
| 16 Jun 2014 | Tornado | EF1 | $100K | — | — | — | County |
| 26 Apr 2009 | Tornado | EF1 | $500K | — | — | — | County |
| 25 May 2008 | Tornado | EF1 | $100K | — | — | — | County |
| 25 May 2008 | Tornado | EF1 | $100K | — | — | — | County |
| 31 Mar 2007 | Tornado | EF1 | $162K | — | — | — | County |
| 26 Aug 2004 | Tornado | F1 | $75K | $20K | — | — | County |
| 1 Jun 2001 | Tornado | F0 | — | — | — | — | County |
| 10 May 2001 | Tornado | F0 | — | — | — | — | County |
| 14 May 1991 | Tornado | F0 | $3K | — | — | — | County |
| 14 May 1991 | Tornado | F1 | $25K | — | — | — | County |
| 8 Apr 1991 | Tornado | F0 | $250 | — | — | — | County |
| 22 Mar 1991 | Tornado | F2 | $250K | — | — | 1 | County |
| 22 Mar 1991 | Tornado | F0 | $3K | — | — | — | County |
| 2 Jun 1990 | Tornado | F2 | $250K | — | — | — | County |
| 13 Mar 1990 | Tornado | F4 | $25M | — | — | — | County |
| 15 Nov 1988 | Tornado | F2 | $250K | — | — | — | County |
| 8 May 1988 | Tornado | F0 | $25K | — | — | — | County |
| 8 May 1988 | Tornado | F0 | $25K | — | — | — | County |
| 7 Aug 1986 | Tornado | F1 | $25K | — | — | 3 | County |
| 24 Aug 1985 | Tornado | F0 | — | — | — | — | County |
| 14 Aug 1985 | Tornado | F0 | — | — | — | — | County |
| 16 May 1977 | Tornado | — | — | — | — | — | County |
| 12 Aug 1974 | Tornado | F4 | $2.5M | — | — | 12 | County |
| 12 Jul 1971 | Tornado | F3 | $2.5M | — | — | 2 | County |
| 26 Jun 1969 | Tornado | F2 | $250K | — | — | — | County |
| 15 Jun 1966 | Tornado | F0 | $30 | — | — | — | County |
| 4 May 1964 | Tornado | F2 | $250K | — | — | 2 | County |
| 15 Nov 1960 | Tornado | F2 | $250K | — | — | — | County |
Questions and answers
How many tornado events has Delaware County had?
40 events in the NCEI Storm Events record between 1950 and 2026. Reporting of tornadoes became far more complete after 1996, so early decades undercount.
When was the last recorded tornado event in Delaware County?
14 Apr 2026 (Tornado, EF1). Records reach NCEI about 120 days after the month ends.
What was the most damaging tornado event recorded in Delaware County?
The tornado of 13 Mar 1990, with property damage estimated by NCEI at $25M.
How does Delaware County compare with Iowa for tornado?
6.9 events per 100 square miles against 6.3 statewide; the county holds 40 of the state's 3,501 recorded events.
Provenance
NOAA NCEI Storm Events Database, yearly details files through 30 Jun 2026, public domain. County-recorded events plus zone-recorded events whose forecast zone is named for the county (marked "Forecast zone"). Population and area from the US Census Bureau (2021). Built 1 Oct 2026. See the methodology, the Tornado hub and the county page.