Delaware County

Every recorded tornado

1. Injuries and deaths are for the tornado’s whole path, which may extend beyond the county. Deaths recorded within Delaware County: 0.
2. Weak tornadoes were under-recorded before Doppler radar coverage became national in the early 1990s, so earlier decades read low. Ratings use the Fujita scale before February 2007 and the Enhanced Fujita scale after.

Storm Prediction Center severe weather database, 1950 to 2025.

Smoke overhead

1. A smoke day is a date on which a smoke plume traced by NOAA Hazard Mapping System analysts from satellite imagery covered this place's point (the county's population centre or the city centre). Counts here are of medium or heavy smoke. Since 2018 analysts have often drawn light smoke as one area over most of the continent, so light-smoke counts are not comparable from year to year. The plumes show smoke anywhere in the air above, not air quality at the ground, and smoke hidden by cloud is missed.

NOAA Hazard Mapping System smoke analysis, 2011 to 2026, retrieved October 30, 2026.

Claims by ZIP code

This product uses the Federal Emergency Management Agency's OpenFEMA API, but is not endorsed by FEMA. The Federal Government or FEMA cannot vouch for the data or analyses derived from these data after the data have been retrieved from the Agency's website(s).

OpenFEMA NFIP Redacted Claims v3, refreshed August 4, 2026. NOAA Storm Events through 2026.

River crests

River gauges

1. Crests are the highest and the recent crests the National Weather Service lists for each river gauge in the county that has a flood stage, not every flood. Flood categories use each gauge's current flood stages; crests from before levees, dams or channel changes may not be comparable. Crests measured on an old datum are left out of the rankings.

NOAA National Water Prediction Service gauge records, retrieved October 30, 2026.

1. The Palmer Drought Severity Index is computed by NOAA each month from the county's average temperature and precipitation, relative to the county's own climate. Zero is normal; -3 or lower is severe drought and -4 or lower extreme drought. It describes the long-term balance of moisture, not water supply or crop losses.

NOAA NCEI nClimDiv county Palmer Drought Severity Index, 1895 to September 2026, issued October 6, 2026.

More event types since 1996

Costliest events since 1996

1. Jul 24, 2010Flash Flood$25.0 million
   National Weather Service narrative

   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…

2. Jul 23, 2010Flood$25.0 million
   National Weather Service narrative

   After about 10 inches of rain fell in the upper Maquoketa River basin, the river surged to record stage levels. ||The initial impact off the surging river levels was seen in Manchester, where portions of the business district as well as numerous homes were affected by flood waters. With water reaching near the rooftops of at least one business, West Main Street was particularly hard-hit, with 2 fast food restaurants, a car dealership, a pharmacy, and several other businesses succombing to the flood waters. Numerous basements filled with water, and there were reports of several basement walls that had collapsed. One man experienced a near-miss when a sinkhole developed in a parking…

3. Jun 1, 2008Flood$4.2 million
   National Weather Service narrative

   Major to record flooding occurred during the month of June 2008 with most forecast points above flood stage for the majority of the month. The flooding during this month was more prolific and severe than the flooding in April 2008, and the flooding in April had been the most prolific flood event since 1997.||While some locations were still experiencing flooding as June began, many of the tributary rivers to the Mississippi in Iowa rose above flood stage during the first few days of the month. At locations that were already above flood stage, the rivers stopped their fall and began climbing again.||Persistent heavy rain from late May into early June resulted in record crests on the…

4. May 17, 2000Hail$4.0 million
   National Weather Service narrative

   A stationary front extended from the plains across Southern Iowa into Central Illinois. The boundary separated cool air to the north from warm air to the south. Morning temperatures ranged from the upper 40s over Southern Wisconsin to the middle 60s over Southeast Iowa and Central Illinois. A cluster of thunderstorms developed during the morning over Northeast Iowa from near Waterloo to Independence. As these storms moved east into Delaware and Dubuque counties they became severe, producing large hail. Hail the size of golfballs battered the city of Manchester for 10 minutes causing extensive damage to cars, trees and several roofs. Damage affected virtually every vehicle parked…

5. May 10, 2003Thunderstorm Wind$2.0 million
   National Weather Service narrative

   A supercell thunderstorm associated with the larger severe weather outbreak of May 10th developed in the evening and moved across Delaware county. A severe macroburst developed just south and east of Manchester, Iowa and produced winds of hurricane force. Three farms were damaged along with numerous trees at the golf course. On U.S. 20 just east of town, power poles were snapped with wires dangling low enough to interfere with vehicle traffic.

6. Oct 7, 2007Flash Flood$500,000
   National Weather Service narrative

   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.

7. Apr 26, 2009Tornado$500,000
   National Weather Service narrative

   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.

8. Jul 24, 2009Hail$250,000
   National Weather Service narrative

   Hail the size of a golf ball fell in about 2 miles north of Delaware, IA around 228 pm July 24. Several houses near Highway 38 just north of town sustained broken windows and siding damage due to the hail.

9. Jun 19, 2009Thunderstorm Wind$250,000
   National Weather Service narrative

   Wind gusts estimated to be 75 mph destroyed some large grain bins at the Ryan, IA COOP around 803 am June 19. In addition, several trees were blown down in town and roof damage was widespread. This report was relayed by the Emergency Manager.

10. Mar 31, 2007Tornado$162,000
    National Weather Service narrative

    This tornado began 5.4 miles north of Delaware, in Delaware county, at about 429 pm CST, and crossed into Clayton county 6 miles east of Edgewood at approximately 437 pm CST. The tornado was rated EF1 (NWS storm survey team), moved north-northeast at 50 mph, and had a total path length of 10 miles and was 200 yards wide. The tornado struck eight farmsteads in Delaware county, producing mostly minor damage to outbuildings and trees. However, at a farm southeast of Greeley, EF1 damage occurred with winds estimated at 81 mph. A dairy barn collapsed, trapping two people that were milking cows under the debris. They were rescued unharmed, but 24 cows were killed. A two-car garage was…

1. Storm Events records before 1996 cover only tornadoes, thunderstorm wind and hail. Damage figures are as reported by the National Weather Service at the time, not adjusted for inflation.

NOAA NCEI Storm Events Database, 1950 to 2026, issued October 26, 2026.

All-time high

102°F3 times, most recently Aug 24, 2023

All-time low

−36°FJan 16, 2009

Warmest night

78°FJun 23, 2025

Coldest day

−19°FFeb 3, 1996

Wettest day

6.22 inAug 1, 2026

Snowiest day

11.2 inDec 9, 2009

Hottest year

1998mean 50.5°F

Coldest year

2014mean 43.2°F

Wettest year

200852.68 in

Driest year

198823.05 in

Snowiest season

65.2 in2007-08

Station Manchester #2 (USC00135086), 924 ft elevation, 3.5 miles from the population centre. Daily records from 1976 to October 27, 2026; 99.5% of days in the last 30 years are complete. Records at a single station can differ from a city’s official threaded record, which may combine several stations.

NOAA NCEI Global Historical Climatology Network Daily.

This product uses the Federal Emergency Management Agency's OpenFEMA API, but is not endorsed by FEMA. The Federal Government or FEMA cannot vouch for the data or analyses derived from these data after the data have been retrieved from the Agency's website(s).

OpenFEMA Disaster Declarations Summaries, retrieved October 30, 2026. Statewide declarations are not listed.

Neighbouring counties

• Tornadoes NOAA Storm Prediction Center severe weather database, through 2025.
• Tropical cyclones NOAA National Hurricane Center HURDAT2 (Atlantic; Northeast and Central Pacific), through 2025.
• Wildfire USGS/USFS Monitoring Trends in Burn Severity, through 2026.
• Storm events NOAA NCEI Storm Events Database, through 2026.
• Flood insurance OpenFEMA NFIP Redacted Claims v3, refreshed August 4, 2026.
• Declarations OpenFEMA Disaster Declarations Summaries v2, retrieved October 30, 2026.
• Weather records NOAA NCEI Global Historical Climatology Network Daily, station USC00135086.
• River crests NOAA National Weather Service, National Water Prediction Service river gauges, retrieved October 30, 2026.
• Drought NOAA NCEI nClimDiv county Palmer Drought Severity Index, through September 2026.
• Smoke NOAA NESDIS Hazard Mapping System smoke analysis, retrieved October 30, 2026.
• Earthquakes USGS ANSS Comprehensive Earthquake Catalog (ComCat), retrieved October 30, 2026.

Joins, thresholds and known limits are set out in the methodology. Found an error? Report it. Page built October 30, 2026.