Alert archive / Delaware / Flash Flood Warnings in 2026

Flash Flood Warning 126, NWS Philadelphia/Mount Holly

August 23, 2026New Castle County, Delaware; Delaware County, Pennsylvania

NWS Philadelphia/Mount Holly issued this flash flood warning at Aug 23, 2026, 3:32 AM EDT for New Castle County, Delaware; Delaware County, Pennsylvania. It was in force for 3 hr. 2 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: Aug 23, 2026, 3:32 AM EDT (07:32 UTC)
Expired: Aug 23, 2026, 6:29 AM EDT
In force: 3 hr
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon
Flood severity: None

Counties New Castle County, DE, Delaware County, PA

The radar

The Philadelphia radar (KDIX), 85 km from the middle of the area, began a volume at 07:34 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
Aug 23, 3:35 AM EDT	FLASH FLOOD	South Chester, PA	Water rescue was reported on 291 near the on ramp for 322 in Chester.
Aug 23, 4:00 AM EDT	FLASH FLOOD	Eddystone, PA	Flooding was reported on Interstate 95 northbound near the 476 interchange.

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

The nearest sounding before it

Washington/Dulle, VA (KIAD), launched 00:00Z, 7.5 hours before the alert went out and 198 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: 653 J/kg
Mixed-layer CIN: -3 J/kg
Mixed-layer LCL: 773 m above ground
0-6 km bulk shear: 34 kt
0-1 km storm-relative helicity: 53 m²/s²
0-3 km storm-relative helicity: 100 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 1.1

Open this sounding in Storm Lab

The text

As transmitted.

600 
WGUS51 KPHI 230732
FFWPHI
DEC003-PAC045-231145-
/O.NEW.KPHI.FF.W.0126.260823T0732Z-260823T1145Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Mount Holly NJ
332 AM EDT Sun Aug 23 2026

The National Weather Service in Mount Holly has issued a

* Flash Flood Warning for...
  Northeastern New Castle County in northern Delaware...
  Southeastern Delaware County in southeastern Pennsylvania...

* Until 745 AM EDT.

* At 332 AM EDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Up to 1 inch of rain has 
  fallen. The expected rainfall rate is 1 to 2 inches in 1 hour. 
  Additional rainfall amounts up to 1 inch 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...
  Philadelphia, Wilmington, Chester, Yeadon, Carneys Point, 
  Folcroft, Swarthmore, Penns Grove, Arden, Chester Township, 
  Chelsea and Nether Providence Township.

This includes the following highways...
	Interstate 476 in Pennsylvania between mile markers 0 and 7.
	Interstate 95 in Pennsylvania between mile markers 0 and 9.
	Interstate 95 in Delaware between mile markers 15 and 23.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Be especially cautious at night when it is harder to recognize the 
dangers of flooding.

Please report observed flooding to local emergency services or law 
enforcement and request they pass this information to the National 
Weather Service when you can do so safely.

&&

LAT...LON 3997 7533 3991 7525 3989 7526 3985 7532
      3985 7534 3980 7541 3978 7544 3976 7546
      3974 7547 3971 7552 3979 7560

FLASH FLOOD...RADAR INDICATED
EXPECTED RAINFALL RATE...1-2 INCHES IN 1 HOUR

$$

MPS

2 follow-up statements

594 
WGUS71 KPHI 230856
FFSPHI

Flash Flood Statement
National Weather Service Mount Holly NJ
456 AM EDT Sun Aug 23 2026

DEC003-PAC045-231145-
/O.CON.KPHI.FF.W.0126.000000T0000Z-260823T1145Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
New Castle DE-Delaware PA-
456 AM EDT Sun Aug 23 2026

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 745 AM EDT THIS 
MORNING FOR NORTHEASTERN NEW CASTLE AND SOUTHEASTERN DELAWARE 
COUNTIES...

At 456 AM EDT, Thunderstorms produced heavy rain in the warned area, 
with flash flooding reported in Chester. Between 1 and 2 inches of 
rain have fallen. While the heavy rain has ended, flash flooding is 
occurring.

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...
  Philadelphia, Wilmington, Chester, Yeadon, Carneys Point, 
  Folcroft, Swarthmore, Penns Grove, Arden, Chester Township, 
  Chelsea and Nether Providence Township.

This includes the following highways...
	Interstate 476 in Pennsylvania between mile markers 0 and 7.
	Interstate 95 in Pennsylvania between mile markers 0 and 9.
	Interstate 95 in Delaware between mile markers 15 and 23.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Be especially cautious at night when it is harder to recognize the 
dangers of flooding.

Please report observed flooding to local emergency services or law 
enforcement and request they pass this information to the National 
Weather Service when you can do so safely.

&&

LAT...LON 3997 7533 3991 7525 3989 7526 3985 7532
      3985 7534 3980 7541 3978 7544 3976 7546
      3974 7547 3971 7552 3979 7560

FLASH FLOOD...RADAR INDICATED

$$

MPS

135 
WGUS71 KPHI 231029
FFSPHI

Flash Flood Statement
National Weather Service Mount Holly NJ
629 AM EDT Sun Aug 23 2026

DEC003-PAC045-231039-
/O.CAN.KPHI.FF.W.0126.000000T0000Z-260823T1145Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
New Castle DE-Delaware PA-
629 AM EDT Sun Aug 23 2026

...FLASH FLOOD WARNING IS CANCELLED FOR NORTHEASTERN NEW CASTLE AND 
SOUTHEASTERN DELAWARE COUNTIES...

Flood waters have receded. The heavy rain has ended. Flooding is no 
longer expected to pose a threat. Please continue to heed remaining 
road closures.

&&

LAT...LON 3997 7533 3991 7525 3989 7526 3985 7532
      3985 7534 3980 7541 3978 7544 3976 7546
      3974 7547 3971 7552 3979 7560

$$

MPS

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 23, 3:49 AM EDT	Flash Flood Warning	PHI	Bucks, Chester, Delaware, Montgomery, Philadelphia	3 hr

Nearby

Flash Flood Warnings in Delaware, 2026 Flash Flood Warnings in Pennsylvania, 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.