Mercer County

Every recorded tornado

1. Injuries and deaths are for the tornado’s whole path, which may extend beyond the county. Deaths recorded within Mercer 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.

Every storm within 100 miles

1. Tropical storms and hurricanes (34 kt or more, still tropical) at closest approach. Post-tropical remnants with gale-force winds are listed but not counted. Direct: track within 50 miles; near: within 100 miles. Distance is measured to the county boundary for counties and to the city centre for cities, using positions interpolated hourly between HURDAT2 fixes.

National Hurricane Center HURDAT2, 1851 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.

Every earthquake of magnitude 4 or more within 50 miles

1. Earthquakes of magnitude 2.5 or more in the USGS Comprehensive Catalog since 1900. Within 50 miles means the epicentre lies within 50 miles of the county boundary (or inside the county).
2. Small earthquakes were under-recorded before the modern seismic networks of the 1970s and are still missed in remote areas, so early decades read low. Magnitudes are as the catalogue reports them and mix scales (moment, local and body-wave).

USGS ANSS Comprehensive Earthquake Catalog, 1900 to present, retrieved October 30, 2026.

Mapped landslides

Mapped by NJ GS (1).

Deadly landslides

1. Landslides mapped in the USGS compilation of landslide inventories across the United States (version 3.0, 2025), rated probable or better. The compilation joins inventories made by federal and state agencies for different purposes and areas, so the number mapped in a county reflects how closely it has been surveyed as much as how often its slopes fail. An area with few records may simply not have been mapped. Deaths are as recorded in the inventories; a slide listed in two inventories is counted once.

USGS Landslide Inventories across the United States, version 3.0, retrieved October 27, 2026.

More event types since 1996

Costliest events since 1996

1. Oct 29, 2012High Wind, Mercer$100 million
   National Weather Service narrative

   Post Tropical Storm Sandy was the costliest natural disaster by far in the state of New Jersey. Record breaking high tides and wave action combined with sustained winds as high as 60 to 70 mph with wind gusts as high as around 90 mph to batter the state. Statewide, Sandy caused an estimated 29.4 billion dollars in damage, destroyed or significantly damaged 30,000 homes and businesses, affected 42,000 additional structures and was responsible directly or indirectly for 38 deaths. A new temporary inlet formed in Mantaloking (Ocean County) where some homes were swept away. About 2.4 million households in the state lost power. It would take two weeks for power to be fully restored to…

2. Aug 28, 2011Flood$75.0 million
   National Weather Service narrative

   In Princeton, a 39-year-old emergency responder died from injuries sustained while investigating a submerged vehicle in flood waters. No one was in the vehicle. In Lawrence Township, a 50-year-old man became trapped in a sewer pipe at Shemin Nurseries and drowned. Flooding along the Delaware River and Assunpink Creek affected Trenton and northeast rail service. The Island and Glen Afton sections of Trenton was affected by flooding from the Delaware River. The Island section was under mandatory evacuation. About 70 homes were damaged and 50 were declared uninhabitable. Flooding along the Assunpink Creek inundated the Trenton Rail station and canceled Amtrak Rail Service between…

3. Sep 1, 2021Flash Flood$50.0 million
   National Weather Service narrative

   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).

4. Sep 16, 1999Flash Flood$32.0 million
   National Weather Service narrative

   Hurricane Floyd battered New Jersey (especially the central and northern thirds) on September 16th and brought with it torrential and in some areas, unprecedented and record breaking rains and damaging winds. The hurricane will go down in history as the greatest natural disaster to ever effect the state of New Jersey to date. Preliminary damage estimates for the entire state were 1.1 billion dollars hitting Bergen and Somerset Counties the hardest. Manville and Bound Brook were hardest hit within Somerset County. Six persons died in the state; all drownings: two each in Somerset and Bergen Counties, one in Passaic County and one in Salem County. Hundreds were injured. The…

5. Jun 28, 2006Flood$8.5 million
   National Weather Service narrative

   Several days of heavy rain throughout the Delaware River Basin culminated with major flooding along the Delaware River from the 28th through the 30th. It was the fourth or fifth highest crest on record for the Delaware River along Mercer County. The crest was slightly lower than the April 2005 flood. President George W. Bush declared Mercer County a disaster area. Sporadic periods of heavy rain started on the 23rd, but the most widespread and heaviest rain fell from the night of the 27th into the morning of the 28th. Event totals in Mercer County averaged three to six inches, but storm totals exceeded 10 inches in parts of the Upper Delaware Basin in New York State. The hardest…

6. Jun 12, 1996Flash Flood$8.0 million
   National Weather Service narrative

   Nearly stationary thunderstorms dropped between 3.5 and 7.6 inches of rain within four hours in western Mercer County. This caused widespread flash flooding throughout the area. Nearly every roadway was flooded. The 7.6 inches of rain represents about a daily one hundred year storm. No one was killed or seriously injured, but about 8 million dollars in property damage occurred, most of it in Ewing. One bridge was washed out. Over 100 homes, 10 apartment buildings and numerous businesses suffered flood damage. The county was declared a major disaster area.In Ewing, the Shabakunk Creek was the major culprit. It made an island out of Fleetwood Village and flooded over 100 homes.…

7. Apr 2, 2005Flood, Mercer$5.0 million
   National Weather Service narrative

   For the second time within seven months a greater than 50-year storm affected the Delaware River Basin and its tributaries. But, this time flooding also extended into the Passaic River Basin. In all, about 6,000 persons were evacuated along the Delaware and Passaic River Basins in New Jersey with about 3,200 homes damaged. New Jersey Acting Governor Richard J. Codey declared a state of emergency on April 3rd. Many homes and businesses that were flooded because of the remnants of Hurricane Ivan along the Delaware River, were flooded again. The crests along the Delaware River were even higher than in September 2004 and were the highest crests since 1955. In many places, it was the…

8. Apr 15, 2007Flood$5.0 million
   National Weather Service narrative

   The combination of poor drainage, basement and waterway flooding caused a driving nightmare in Mercer County. Many major roadways in the county were flooded and closed in sections including U.S. Routes 1, 130 and 206 and New Jersey State Route 33. There were still about 10 roadways closed on the evening of the 17th. It was estimated that over 1,000 basements were flooded in the county. Flooding waterways included the Assunpink, Little Brook and Stony Brook. In Trenton, Assunpink Creek flooding affected eight homes on Mulberry Street. North Olden Street was also flooded by the creek. In West Windsor, thousands of historical papers and other artifacts were damaged when water flooded…

9. Sep 19, 2004Flood, Mercer$2.4 million
   National Weather Service narrative

   The remnants of Hurricane Ivan interacting with a slowly moving cold front caused widespread very heavy in the upper and middle sections of the Delaware River Valley. While the rain was not heavy in Mercer County, the runoff from the heavy rain upstream produced the worst flooding along the Delaware River since 1955. Townships and roadways along the Delaware River were hardest hit. Damage was estimated in the millions. The Delaware River at Washington's Crossing was above its 20 foot flood stage from 416 p.m. EDT through 828 p.m. EDT on the 19th. It crested at 20.12 feet at 5 p.m. EDT. Farther downstream, the Delaware River at Trenton was above its 20 foot flood stage from 148…

10. Sep 8, 2011Flood$2.0 million
    National Weather Service narrative

    Eighty-three homes were damaged by the flooding associated with Lee in Mercer County. Six homes suffered major damage, seventy-two minor damage and five more were affected by flood waters. In Trenton, about 250 people were evacuated from their homes in the Island and Glen Afton section of the city. Flooding was also reported along North Clinton Avenue. State workers were dismissed early on the 8th. New Jersey State Route 29 was closed in Trenton and Ewing. Some schools near the Delaware River were closed on the 9th. In Lawrence Township, a voluntary evacuation occurred near Quaker Road because of a pre-existing breach on the Delaware and Raritan canal that was bringing in flood…

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

106°FJul 22, 2011

All-time low

−2°FJan 7, 2018

Warmest night

83°FJul 23, 2011

Coldest day

11°FJan 7, 2014

Wettest day

7.25 inSep 16, 1999

Snowiest day

16.7 inJan 23, 2016

Hottest year

2012mean 57.1°F

Coldest year

2003mean 51.9°F

Wettest year

201862.96 in

Driest year

202534.55 in

Snowiest season

54.3 in2013-14

Station Trenton-mercer Airport (USW00014792), 190 ft elevation, 6.3 miles from the population centre. Daily records from 1945 to October 26, 2026; 95.4% 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 USW00014792.
• 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.
• Landslides USGS Landslide Inventories across the United States, version 3.0 (2025).
• 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.