74
Recorded events
2
Direct deaths
6
Direct injuries
$93.3M
Property damage
Flash Flood in Mercer County, New Jersey: 74 recorded events between 1996 and 2024. The strongest on record measured 0. That places the county #307 nationally and #11 statewide for this hazard.
Decade by decade
Flash Flood in Mercer County, New Jersey: events per decade
Reporting practice changed over time — early decades are undercounted, not calmer.
The busiest decade for flash flood in Mercer County is the 1990s, when 22 of the county's 74 recorded events were logged. Comparing decades is useful for spotting active periods, but the earliest years are thin because systematic reporting for this hazard began later.
Within the Mercer County archive, flash flood makes up 13.8% of all recorded severe weather across 8 hazard types. Nationally the county sits at #307 for this hazard and #11 within New Jersey, putting it in the 90.0 percentile of all U.S. counties.
Seasonality
Events by month
Aug is the peak month for flash flood in Mercer County with 18 recorded events, while Feb is the quietest. Seasonality here is a property of the archive as much as the climate: reports cluster where population and spotter networks are densest.
Significant events
Deadliest on record
| Date | Location | Scale | Deaths | Injuries | Damage |
|---|---|---|---|---|---|
| Sep 1, 2021 | TITUSVILLE | 0 | 2 | 0 | $50.0M |
| Sep 16, 1999 | COUNTYWIDE | 0 | 0 | 5 | $32.0M |
| May 24, 1999 | CENTRAL PORTION | 0 | 0 | 1 | $0 |
Most recent
Latest recorded events
| Date | Location | Magnitude | Damage |
|---|---|---|---|
| Aug 6, 2024 | EWING TOWNSHIP | 0 | $40K |
| Aug 6, 2024 | PENNINGTON | 0 | $0 |
| Jul 15, 2023 | PENNINGTON | 0 | $0 |
| Jul 15, 2023 | SOMERSET | 0 | $0 |
| Oct 26, 2021 | PENNS NECK | 0 | $0 |
| Sep 23, 2021 | PENNS NECK | 0 | $0 |
| Sep 1, 2021 | TITUSVILLE | 0 | $50.0M |
| Aug 22, 2021 | TRENTON | 0 | $0 |
| Aug 22, 2021 | GROVERS MILLS | 0 | $0 |
| Aug 22, 2021 | MERCERVILLE | 0 | $0 |
Other hazards here
More from Mercer County
- Thunderstorm Wind 269
- Hail 63
- Heavy Rain 42
From the record
What the reports say
Written by National Weather Service staff at the time of the event · public domain
Widespread flash flooding occurred in Mercer County with numerous road closures and nearly 100 water rescues. There were two flood related fatalities in the county, both in Hopewell Township. Many waterways overflowed their banks including the Assunpink Creek, Stony Brook and the Delaware River (with a highly unusual quick response to the runoff).
Multiple roads were flooded and impassable including US 1, Route 571, Washington and Alexander roads. Water rescues ongoing in Princeton. Canal Pointe Blvd also was closed due to flooding/ Several people were trapped in cars and needed to be rescued.
Thunderstorms with torrential downpours damaged a home in Hamilton Township, flooded and closed U.S. Route 206 in Lawrence Township and caused flooding along the Assunpink Creek. In Hamilton Township, a home on Evergreen Avenue became structurally unsound after its basement foundation collapsed. Several other homes in the area also had flooded basements. In Lawrence Township, U.S. Route 206 was flooded near Notre Dame High School. The Assunpink Creek at Trenton was above its 8.5 foot flood stage from 312 p.m. EDT through 801 p.m. EDT on the 2nd. It crested at 8.96 feet at 630 p.m. EDT. Event totals included 3.54 inches in Lawrence Township, 2.51 inches in Hamilton Township and 2.15 inches in Hightstown.
Quick answers
Frequently asked
How many flash flood events are on record in Mercer County, New Jersey?
74 flash flood events are recorded in Mercer County between 1996 and 2024, causing 2 direct deaths.
What is the strongest flash flood recorded in Mercer County?
The strongest flash flood on record in Mercer County measured 0.
Where does the flash flood data for Mercer County come from?
All events come from the NOAA/NCEI Storm Events Database, the federal public-domain archive of severe weather reports. Dates are UTC, damage is as reported and not inflation-adjusted, and the most recent entries may still be revised.
Cite this page
“Flash Flood in Mercer County, New Jersey.” Severe Weather History. severeweatherhistory.com/county/new-jersey/mercer-county/flash-flood/ · Data: NOAA/NCEI, FEMA, U.S. Census — public domain.