Flash Flood in Delaware
Every flash flood event the National Weather Service has filed in Delaware, year by year, with the most significant episodes. Flooding that begins within six hours of the rain that causes it, or of a dam or levee failure or ice jam release, often with deadly speed.
The most significant on the map
The most significant flash flood episodes in Delaware.
- Tornadoes
- Tropical storms and surge
- Floods
- Wind
- Hail
- Winter weather
- Heat and drought
- Cold
- Fire, smoke and dust
- Marine and coastal
- Other
The record
- Events
- 255
- Deaths
- 4
- Injuries
- 6
- Damage
- $32 million
Every year
The most significant
Ranked by deaths, injuries, damage and size together.
- Hurricane and Flash Flooding in Delaware, September 16 to 17, 1999Hurricane Floyd battered Delaware (especially New Castle County) on September 16th and brought with it torrential rains and damaging winds.
- Tornado and Tropical Storm in Delaware, August 27 to 30, 2011Hurricane Irene produced heavy flooding rain, widespread tropical storm force wind gusts, a confirmed tornado near Lewes in Sussex County, moderate to severe coastal flooding and beach erosion and caused two flooding related deaths, forced evacuations near the coast over the…
- Tropical Storm and Storm Surge in Delaware, September 18 to 20, 2003Tropical Storm Isabel caused tidal flooding up Delaware Bay, heavy rain and strong power outage producing winds. Isabel made landfall as a hurricane near Drum Inlet, North Carolina around 100 p.m. EDT on the 18th and weakened as it tracked farther inland.
- Flash Flood in Delaware, September 15 to 16, 2003Remnant moisture from Tropical Storm Henri produced copious amounts of rain during the early morning of the 15th across northern New Castle County and hit Mill Creek Hundred in the northwest part of the county the hardest.
- Flash Flood and Flooding in Delaware, September 29 to 30, 2016A slow moving frontal boundary coupled with tropical moisture advecting northward ahead of the front led to rounds of heavy showers in Delaware from the 27th into the next couple of days.
- Flash Flood in Delaware, September 1, 2021Post Tropical Cyclone Ida brought heavy rain to much of Delaware on September 1. Rainfall totals were as high as 2 to 6 inches. The heavy rain resulted in flash flooding in the northern part of the state.
- Tornadoes and Tropical Storm in Delaware, August 4, 2020Tropical Storm Isaias brought high winds, heavy rain, several tornadoes, and coastal flooding to the mid-Atlantic region, becoming the most impactful tropical cyclone to impact most of the region since Sandy in 2012.
- Flash Flood in Delaware, August 11 to 12, 2001Slow moving thunderstorms with torrential rains inundated southwestern Sussex County during the late afternoon of the 11th. Doppler Radar storm total estimates reached 8.4 inches around Seaford.
- Flash Flood and Flood in Delaware, June 25 to 26, 2006Repeating thunderstorms with torrential downpours dropped a Doppler Radar estimated six to eight inches of rain across southwestern parts of Sussex County during the morning of the 25th. This caused extensive roadway, field and stream flooding.
- Flash Flooding in Delaware, August 25 to 26, 2012A series of slow moving thunderstorms associated with a nearly stationary low pressure system in Eastern Virginia caused flash flooding in Sussex County that started overnight on the 25th and lasted into the 26th. Doppler Radar storm total estimates reached around 8.5 inches.
- Flash Flood in Delaware, July 12 to 13, 2004A series of thunderstorms with torrential downpours caused flooding from Clayton and Smyrna southeast through Dover. Hardest hit was Smyrna which declared a state of emergency after 11.10 inches of rain fell. This represents approximately a once in five hundred year storm.
- Flash Flood in Delaware, June 19 to 20, 1996Slow moving thunderstorms with torrential downpours washed out two bridges and caused widespread street and highway flooding in the northern part of the county. Many roads were closed. Dover reported 3.11 inches of rain. One bridge washed out near Cheswold.
- Tornado and Flash Flooding in Delaware, August 8, 2024Showers and thunderstorms developing along a stationary front resulted in a few showers and thunderstorms developing. A few storms were severe producing damaging wind gusts and a tornado. Additionally training storms led to flash flooding in northern Delaware.
- Flash Flooding in Delaware, July 9, 2025A slow-moving cold front produced heavy rain and flash flooding across portions of the region.
- Tornado and Flash Flooding in Delaware, August 7, 2020An impulse riding along a west to east boundary stalled near the Mason-Dixon line produced severe thunderstorms and heavy rain across sections of northern Delaware from late afternoon through the evening hours on August 7th.
- Flash Flood in Delaware, July 14, 2010For the second consecutive day, slow moving thunderstorms with heavy rain caused heavy rain and flash flooding in New Castle County. Doppler Radar storm total estimates reached 3.5 inches north of Wilmington.
- Flash Flooding and Flood in Delaware, July 12 to 13, 2013A low pressure system that formed on a frontal boundary helped produce showers and thunderstorms with very heavy downpours and led to flooding and flash flooding in Delaware.
- Flash Flooding in Delaware, July 31, 2025A stationary front sparked off showers and thunderstorms across the forecast area. Flash flooding resulted.
- Flash Flooding and Flood in Delaware, July 22 to 24, 2017A stalled frontal boundary was the focus for several rounds of thunderstorms that produced damaging winds and flooding in spots.
- Flash Flooding and Flooding in Delaware, July 6 to 7, 2017A stationary frontal boundary draped across the Delmarva lead to a period of heavy rainfall during the afternoon and evening of July 6th, particularly over northern Delaware and northeast Maryland.
- Flash Flood in Delaware, January 18, 1999The combination of showers and thunderstorms with heavy rain and the already saturated ground caused flooding along some of the river and streams across northern New Castle County. The Christina River at Coochs Bridge was above its 9 foot flood stage from 5 p.m. through 9 p.m.
- Flash Flood in Delaware, July 12, 2004A series of thunderstorms with torrential rain caused widespread poor drainage flooding and flooding of rivers and streams, particularly in the northern part of New Castle County.
- Flash Flooding and Lightning Strike in Delaware, July 13, 2016A stationary front was located across the region on the 13th. This led to the development of showers and thunderstorms during the afternoon and evening hours. These thunderstorms produced heavy rainfall with a few reports of flash flooding.
- Flash Flooding and Damaging Winds in Delaware, August 31, 2018Locally heavy rain produced a swath of 4 to 7 inch rainfall totals from southern New Castle County down to northern Sussex County on the afternoon and evening of August 31. Thunderstorms caused isolated wind damage as well.
- Flash Flood and Damaging Wind in Delaware, August 2 to 3, 2017A hot and humid airmass with weak boundaries led to slow moving strong to severe thunderstorms with damaging winds, hail and flooding.
More
Sources
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24.