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Delaware County, Iowa severe weather history spans 465 recorded events between 1955 and 2026. The dominant hazard is thunderstorm wind, accounting for 47.1% of all recorded events. It ranks #1,002 nationally and #39 in Iowa.
465
Recorded events
0
Direct deaths
22
Direct injuries
$96.1M
Property damage
The record
What the Delaware County, Iowa severe weather history record shows
Across the archive, Delaware County, Iowa severe weather history averages 6.5 recorded events a year. The busiest stretch on record is the 2000s, with 165 events logged in that decade alone. Roughly 74 events fall before 1990 and 391 from 1990 onward — a gap that reflects the expansion of NOAA reporting practice as much as the weather itself.
The costliest is tornado, with $32.7M in reported property damage. In total, 8 distinct hazard types appear in this county archive, each listed with its own dated record below.
By hazard type
Every hazard type recorded in Delaware County
| Hazard | Events | Deaths | Damage | Max | Span |
|---|---|---|---|---|---|
| Thunderstorm Wind | 219 | 0 | $3.7M | 80 | 1955–2026 |
| Hail | 152 | 0 | $4.5M | 4.5 | 1961–2026 |
| Tornado | 40 | 0 | $32.7M | F4 | 1960–2026 |
| Flash Flood | 32 | 0 | $25.7M | 0 | 1997–2026 |
| Flood | 8 | 0 | $29.5M | 0 | 2008–2016 |
| Heavy Rain | 7 | 0 | $5K | 2.37 | 2000–2011 |
| Lightning | 4 | 0 | $30K | 0 | 2006–2022 |
| Funnel Cloud | 3 | 0 | $0 | 0 | 2000–2019 |
Decade by decade
Delaware County, Iowa severe weather history by decade
Reporting practice changed over time — early decades are undercounted, not calmer.
Tornado tracks
Paths crossing this county
47 mapped tornado paths intersect this county: 33 touched down inside it and 14 crossed in from a neighbouring county. This comes from path geometry, not county-tagged reports.
| Date | Scale | Deaths | Injuries | Path length | Origin |
|---|---|---|---|---|---|
| 1990-03-13 | EF4 | 0 | 0 | 19.0 mi | Crossed in |
| 1974-08-12 | EF4 | 0 | 12 | 5.0 mi | Touched down here |
| 1954-04-30 | EF4 | 0 | 0 | 80.4 mi | Crossed in |
| 2008-05-25 | EF3 | 0 | 3 | 32.0 mi | Crossed in |
| 1995-07-27 | EF3 | 0 | 0 | 20.0 mi | Crossed in |
| 1993-06-19 | EF3 | 0 | 0 | 9.0 mi | Touched down here |
| 1971-07-12 | EF3 | 0 | 2 | 0.1 mi | Touched down here |
| 2017-06-28 | EF2 | 0 | 0 | 2.5 mi | Crossed in |
| 1991-03-22 | EF2 | 0 | 1 | 17.0 mi | Touched down here |
| 1990-06-02 | EF2 | 0 | 0 | 10.5 mi | Crossed in |
Significant events
Deadliest events on record in Delaware County
| Date | Type | Location | Deaths | Injuries | Damage |
|---|---|---|---|---|---|
| Aug 12, 1974 | Tornado | 0 | 12 | $2.5M | |
| Aug 7, 1986 | Tornado | 0 | 3 | $25K | |
| May 27, 2006 | Lightning | PETERSBURG | 0 | 2 | $0 |
| Jul 13, 1971 | Tornado | 0 | 2 | $2.5M | |
| May 5, 1964 | Tornado | 0 | 2 | $250K | |
| Mar 23, 1991 | Tornado | 0 | 1 | $250K |
From the record
What the reports say
Written by National Weather Service staff at the time of the event · public domain
Record flooding on the Maquoketa River resulted in the failure of the earthen berm on the south side of the Lake Delhi/Hartwick Lake dam during the late morning and afternoon of July 24. The dam failure resulted in flash flooding of residences along the Maquoketa River immediately downstream of the dam, including portions of Hopkinton. In addition, the dam failure emptied out the 9 mile stretch of the Maquoketa River that constituted Lake Delhi/Hartwick Lake.||In Hopkinton, a few homes, several garages, outbuildings, parks and roads flooded. ||By the time the flood waters reached Monticello, the flood wave from the dam failure had largely been absorbed in the larger crest due to the ongoing record flooding of the Maquoketa River.||Please see the Storm Data narrative for the record flooding on the Maquoketa River for details on the damage due to the flooded Maquoketa River, including the homes at Lake Delhi.
Continued from Linn County. An EF1 tornado with estimated wind speeds of up to 100 mph touched down near Lafayette, IA around 452 pm and proceeded to track northeast crossing the Linn-Delaware County line around 510 pm, finally lifting just north of Buck Creek, IA around 530 pm. Several farms sustained structural and equipment damage, trees were uprooted or snapped off, some camping trailers were destroyed, and several power lines were blown down.
There were several reports of rainfall of 6 inches in the city of Manchester, with a trained spotter measuring 3 inches in one hour. Considerable basement and street flooding occurred, and there was some damage to gravel roads in the surrounding rural areas. Water was knee deep in some parts of the city, and many streets were closed. About 150 homes in the area had basement flooding or damage to foundations. The administration building at Manchester's school bus garage was flooded with two feet of water on the main floor. In only about 3 hours, the city received twice as much rain as it usually gets in the entire month of October.
Context
Risk, population and federal disasters
Relatively Low
FEMA NRI risk rating
17,558
Population (ACS)
$178K
Median home value
18
Federal declarations
| Declared | Incident | Title | Type |
|---|---|---|---|
| Mar 23, 2020 | Biological | COVID-19 PANDEMIC | DR |
| Mar 13, 2020 | Biological | COVID-19 | EM |
| Aug 20, 2018 | Severe Storm | SEVERE STORMS, TORNADOES, STRAIGHT-LINE WINDS, AND FLOODING | DR |
| Oct 31, 2016 | Flood | SEVERE STORMS AND FLOODING | DR |
| Jul 31, 2013 | Severe Storm | SEVERE STORMS, TORNADOES, AND FLOODING | DR |
| Jul 2, 2013 | Severe Storm | SEVERE STORMS, TORNADOES, AND FLOODING | DR |
Within the county
Most affected places
- Manchester 101
Quick answers
Frequently asked
How many severe weather events have been recorded in Delaware County, Iowa?
465 events are on record between 1955 and 2026, causing 0 direct deaths and $96.1M in property damage.
What is the most common severe weather hazard in Delaware County?
Thunderstorm Wind, with 219 recorded events — 47.1% of everything in the archive for this county.
How many tornadoes have crossed Delaware County?
47 mapped tornado paths intersect the county boundary; 33 of them touched down inside it. This is derived from path geometry, not county-tagged reports.
How many federal disaster declarations cover Delaware County?
18 federal disaster declarations from FEMA include Delaware County, each tied to a specific incident period.
How risky is Delaware County compared with the rest of the country?
FEMA's National Risk Index rates Delaware County as relatively low risk, placing it in the 50 percentile of its state for expected annual loss.
Where does the Delaware County, Iowa severe weather history data come from?
Every figure is drawn from United States federal public-domain records: NOAA/NCEI Storm Events for the event archive, NOAA SPC SVRGIS for mapped tornado paths, FEMA for disaster declarations and risk ratings, and the U.S. Census for population context. Dates are shown in UTC and recent entries may still be revised by NOAA.
Nearby
Neighbouring counties
- Decatur County 311
- Des Moines County 492
- Davis County 276
- Dickinson County 487
- Dallas County 964
- Dubuque County 700
Cite this page
“Delaware County, Iowa.” Severe Weather History. severeweatherhistory.com/county/iowa/delaware-county/ · Data: NOAA/NCEI, FEMA, U.S. Census — public domain.