Alert archive / New Jersey / Flash Flood Warnings in 2026

Flash Flood Warning 48, NWS Philadelphia/Mount Holly

July 18, 2026Mercer County, Middlesex County, Somerset County, New Jersey

NWS Philadelphia/Mount Holly issued this flash flood warning at Jul 18, 2026, 1:52 PM EDT for Mercer County, Middlesex County, Somerset County, New Jersey. It was in force for 4 hr. 12 reports came from inside the area while it was in force.

The area

The outline as issued, with what was reported inside it.

The facts

Issued: Jul 18, 2026, 1:52 PM EDT (17:52 UTC)
Expired: Jul 18, 2026, 5:27 PM EDT
In force: 4 hr
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon
Flood severity: None

Counties Mercer County, NJ, Middlesex County, NJ, Somerset County, NJ

The radar

The Philadelphia radar (KDIX), 55 km from the middle of the area, began a volume at 17:52 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

What was reported inside it

Time	Report	Where	Remark
Jul 18, 2:00 PM EDT	FLOOD	Laurence Harbor, NJ	NJDOT reported flooding on NJ 35 Southbound South of CR 689/Lawrence Pkwy (Old Bridge Twp), All lanes closed.
Jul 18, 2:00 PM EDT	FLASH FLOOD	Laurence Harbor, NJ	Corrects previous flood report from Laurence Harbor. NJDOT reported flooding on NJ 35 Southbound South of CR 689/Lawrence Pkwy (Old Bridge Twp), All lanes closed.
Jul 18, 2:20 PM EDT	FLASH FLOOD	South River, NJ	Several roads closed in South River due to flooding.
Jul 18, 2:21 PM EDT	FLOOD	1 Sw Cheesequake, NJ	NJDOT reported flooding on US 9 Northbound At Jake Brown Rd (Old Bridge Twp), All lanes closed.
Jul 18, 2:21 PM EDT	FLASH FLOOD	1 Sw Cheesequake, NJ	Corrects previous flood report from 1 SW Cheesequake. NJDOT reported flooding on US 9 Northbound At Jake Brown Rd (Old Bridge Twp), All lanes closed.
Jul 18, 2:33 PM EDT	FLOOD	1 Ese South River, NJ	Trained spotter reported Whitehead Ave in South River closed due to flooding.
Jul 18, 2:33 PM EDT	FLASH FLOOD	1 Ese South River, NJ	Corrects previous flood report from 1 ESE South River. Trained spotter reported Whitehead Ave in South River closed due to flooding.
Jul 18, 2:40 PM EDT	FLASH FLOOD	Milltown, NJ	Several roads closed in Milltown due to flooding.
Jul 18, 2:44 PM EDT	FLOOD	1 S Heathcote, NJ	NJDOT reported flooding on US 1 Southbound At Raymond Rd (South Brunswick Twp), ramp lane closed.
Jul 18, 2:44 PM EDT	FLASH FLOOD	1 S Heathcote, NJ	Corrects previous flood report from 1 S Heathcote. NJDOT reported flooding on US 1 Southbound At Raymond Rd (South Brunswick Twp), ramp lane closed.
Jul 18, 2:50 PM EDT	FLOOD	1 N Spotswood, NJ	Local news site reported flooding on Old Stage Road and Summerhill Road.
Jul 18, 2:50 PM EDT	FLASH FLOOD	1 N Spotswood, NJ	Corrects previous flood report from 1 N Spotswood. Local news site reported flooding on Old Stage Road and Summerhill Road.

Local storm reports filed while the alert was in force, from inside its polygon or its counties.

The nearest sounding before it

Brookhaven, NY (KOKX), launched 12:00Z, 5.9 hours before the alert went out and 136 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 5 J/kg
Mixed-layer CIN: -238 J/kg
Mixed-layer LCL: 1076 m above ground
0-6 km bulk shear: 45 kt
0-1 km storm-relative helicity: 131 m²/s²
0-3 km storm-relative helicity: 157 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 1.0

Open this sounding in Storm Lab

The text

As transmitted.

188 
WGUS51 KPHI 181752
FFWPHI
NJC021-023-035-182200-
/O.NEW.KPHI.FF.W.0048.260718T1752Z-260718T2200Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Mount Holly NJ
152 PM EDT Sat Jul 18 2026

The National Weather Service in Mount Holly has issued a

* Flash Flood Warning for...
  North Central Mercer County in central New Jersey...
  Central Middlesex County in northern New Jersey...
  South Central Somerset County in northern New Jersey...

* Until 600 PM EDT.

* At 152 PM EDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 1 and 2 inches of rain 
  have fallen. The expected rainfall rate is 1 to 2.5 inches in 1 
  hour. Additional rainfall amounts of 0.5 to 1.5 inches are 
  possible in the warned area. Flash flooding is ongoing or expected 
  to begin shortly.

  HAZARD...Flash flooding caused by thunderstorms.

  SOURCE...Radar.

  IMPACT...Flooding of small creeks and streams, urban areas,
           highways, streets, and underpasses as well as other
           drainage and low lying areas.

* Some locations that may experience flash flooding include...
  Old Bridge, East Brunswick, South Brunswick, Sayreville, North 
  Brunswick, Hopewell, Rocky Hill, Dayton, North Brunswick Township, 
  Kendall Park, Kingston and Brownville.

This includes Garden State Parkway between mile markers 121 and 125.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Turn around...don't drown when encountering flooded roads. Most 
flood deaths occur in vehicles.

&&

LAT...LON 4036 7480 4040 7480 4049 7428 4052 7426
      4051 7425 4050 7426 4050 7427 4048 7427
      4047 7427 4046 7426 4045 7422 4044 7423
      4044 7424 4043 7425 4041 7428 4035 7476

FLASH FLOOD...RADAR INDICATED
EXPECTED RAINFALL RATE...1-2.5 INCHES IN 1 HOUR

$$

Kruzdlo

1 follow-up statement

144 
WGUS71 KPHI 182127
FFSPHI

Flash Flood Statement
National Weather Service Mount Holly NJ
527 PM EDT Sat Jul 18 2026

NJC021-023-035-182137-
/O.CAN.KPHI.FF.W.0048.000000T0000Z-260718T2200Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Mercer NJ-Middlesex NJ-Somerset NJ-
527 PM EDT Sat Jul 18 2026

...FLASH FLOOD WARNING IS CANCELLED FOR NORTH CENTRAL MERCER, 
CENTRAL MIDDLESEX AND SOUTH CENTRAL SOMERSET COUNTIES...

The heavy rain has ended. Flooding is no longer expected to pose a 
threat.

A Flood Watch remains in effect until 200 AM EDT Sunday for portions 
of northern Delaware, New Jersey, and Pennsylvania.

&&

LAT...LON 4036 7480 4040 7480 4049 7428 4052 7426
      4051 7425 4050 7426 4050 7427 4048 7427
      4047 7427 4046 7426 4045 7422 4044 7423
      4044 7424 4043 7425 4041 7428 4035 7476

$$

Kruzdlo

The office that day

Everything else NWS Philadelphia/Mount Holly issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 18, 10:39 AM EDT	Severe Thunderstorm Warning	PHI	Sussex, Warren	21 min
Jul 18, 12:40 PM EDT	Flash Flood Warning	PHI	Middlesex, Morris, Somerset	3 hr
Jul 18, 2:36 PM EDT	Flash Flood Warning	PHI	Hunterdon, Mercer, Middlesex, Monmouth	4 hr
Jul 18, 3:13 PM EDT	Severe Thunderstorm Warning	PHI	Burlington, Mercer, Middlesex, Monmouth, Ocean	47 min
Jul 18, 3:14 PM EDT	Flash Flood Warning Considerable damage threat	PHI	Mercer	4 hr
Jul 18, 3:16 PM EDT	Special Marine Warning	PHI		59 min
Jul 18, 3:30 PM EDT	Severe Thunderstorm Warning	PHI	Burlington, Camden	45 min
Jul 18, 3:31 PM EDT	Severe Thunderstorm Warning	PHI	Burlington, Monmouth, Ocean	44 min
Jul 18, 3:36 PM EDT	Severe Thunderstorm Warning	PHI	Burlington, Camden, Gloucester	39 min
Jul 18, 3:44 PM EDT	Flash Flood Warning	PHI	Middlesex, Monmouth, Ocean	4 hr
Jul 18, 4:02 PM EDT	Special Marine Warning	PHI		118 min
Jul 18, 4:03 PM EDT	Severe Thunderstorm Warning	PHI	Burlington, Ocean	42 min
Jul 18, 4:34 PM EDT	Flash Flood Warning	PHI	Ocean	4 hr
Jul 18, 4:46 PM EDT	Flash Flood Warning	PHI	Ocean	4 hr
Jul 18, 5:14 PM EDT	Severe Thunderstorm Warning	PHI	Cumberland, Salem	61 min
Jul 18, 5:16 PM EDT	Special Marine Warning	PHI		89 min
Jul 18, 5:47 PM EDT	Special Marine Warning	PHI		118 min
Jul 18, 5:49 PM EDT	Severe Thunderstorm Warning	PHI	Monmouth, Ocean	41 min
Jul 18, 6:30 PM EDT	Special Marine Warning	PHI		2 hr
Jul 18, 6:30 PM EDT	Severe Thunderstorm Warning	PHI	Mercer, Middlesex, Monmouth, Somerset	45 min
Jul 18, 6:55 PM EDT	Areal Flood Warning	PHI	Monmouth	4 hr
Jul 18, 6:56 PM EDT	Special Marine Warning	PHI		64 min
Jul 18, 7:13 PM EDT	Severe Thunderstorm Warning	PHI	Cape May	32 min
Jul 18, 7:47 PM EDT	Areal Flood Warning	PHI	Monmouth, Ocean	4 hr

Nearby

Flash Flood Warnings in New Jersey, 2026 Every flash flood warning in 2026

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.