Alert archive / Pennsylvania / Flash Flood Warnings in 2025

Flash Flood Warning 17, NWS Philadelphia/Mount Holly

May 31, 20254 counties in Pennsylvania

NWS Philadelphia/Mount Holly issued this flash flood warning at May 31, 2025, 1:04 AM EDT for 4 counties in Pennsylvania. It was in force for 4 hr. 1 report 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: May 31, 2025, 1:04 AM EDT (05:04 UTC)
Expired: May 31, 2025, 5:15 AM EDT
In force: 4 hr
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon
Flood severity: None

Counties Berks County, PA, Bucks County, PA, Lehigh County, PA, Montgomery County, PA

The radar

The Philadelphia radar (KDIX), 114 km from the middle of the area, began a volume at 05:07 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
May 31, 2:45 AM EDT	FLASH FLOOD	1 S Upper Hanover Twp, PA	East Greenville (EGRP1) went into flood stage.

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, 5.1 hours before the alert went out and 215 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: 926 J/kg
Mixed-layer CIN: -4 J/kg
Mixed-layer LCL: 804 m above ground
0-6 km bulk shear: 48 kt
0-1 km storm-relative helicity: 128 m²/s²
0-3 km storm-relative helicity: 146 m²/s²
Significant tornado parameter: 0.6
Supercell composite: 5.5

Open this sounding in Storm Lab

The text

As transmitted.

477 
WGUS51 KPHI 310504
FFWPHI
PAC011-017-077-091-310915-
/O.NEW.KPHI.FF.W.0017.250531T0504Z-250531T0915Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Mount Holly NJ
104 AM EDT Sat May 31 2025

The National Weather Service in Mount Holly has issued a

* Flash Flood Warning for...
  Eastern Berks County in eastern Pennsylvania...
  Southern Lehigh County in eastern Pennsylvania...
  West Central Bucks County in southeastern Pennsylvania...
  Northwestern Montgomery County in southeastern Pennsylvania...

* Until 515 AM EDT.

* At 104 AM EDT, Doppler radar indicated heavy rain across the 
  warned area. Between 1 and 2 inches of rain have fallen. The 
  expected rainfall rate is 1 to 2 inches in 1 hour. Additional 
  rainfall amounts of 1 to 2 inches are possible in the warned area. 
  Flash flooding is ongoing or expected to begin shortly.

  HAZARD...Flash flooding caused by heavy rain.

  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...
  Allentown, Reading, Norristown, Pottstown, Phoenixville, West 
  Norriton, East Norriton, Emmaus, Wyomissing, Quakertown, Birdsboro 
  and Collegeville.

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.

&&

LAT...LON 4042 7605 4051 7598 4059 7596 4064 7558
      4061 7543 4057 7539 4040 7535 4014 7533
      4013 7549 4014 7551 4016 7550 4015 7552
      4020 7556 4024 7560 4022 7561 4024 7570
      4021 7575 4031 7601

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

$$

Hoeflich

2 follow-up statements

723 
WGUS71 KPHI 310654
FFSPHI

Flash Flood Statement
National Weather Service Mount Holly NJ
254 AM EDT Sat May 31 2025

PAC011-017-077-091-310915-
/O.CON.KPHI.FF.W.0017.000000T0000Z-250531T0915Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Berks PA-Bucks PA-Lehigh PA-Montgomery PA-
254 AM EDT Sat May 31 2025

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 515 AM EDT EARLY THIS 
MORNING FOR EASTERN BERKS, SOUTHERN LEHIGH, WEST CENTRAL BUCKS AND 
NORTHWESTERN MONTGOMERY COUNTIES...

At 254 AM EDT, gauge reports indicated that heavy rain was falling 
as the Perkiomen Creek at East Greenville went into flood stage. 
Between 1.5 and 2.5 inches of rain have fallen. Additional rainfall 
amounts up to 0.5 inches are possible in the warned area. Flash 
flooding is already occurring.

HAZARD...Flash flooding caused by heavy rain.

SOURCE...Gauges reported.

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

For Perkiomen Creek at East Greenville:
At 2:45am the stage was 5.16 feet.
Flood Stage is 5 feet.

For Little Lehigh at Trexlertown near Little Lehigh Creek:
At 2:15am the stage was 3.0 feet.
Flood Stage is 4.5 feet.

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.

&&

LAT...LON 4042 7605 4051 7598 4059 7596 4064 7558
      4061 7543 4057 7539 4040 7535 4014 7533
      4013 7549 4014 7551 4016 7550 4015 7552
      4020 7556 4024 7560 4022 7561 4024 7570
      4021 7575 4031 7601

FLASH FLOOD...GAUGE INDICATED

$$

Hoeflich

220 
WGUS71 KPHI 310908
FFSPHI

Flash Flood Statement
National Weather Service Mount Holly NJ
508 AM EDT Sat May 31 2025

PAC011-017-077-091-310918-
/O.EXP.KPHI.FF.W.0017.000000T0000Z-250531T0915Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Berks PA-Bucks PA-Lehigh PA-Montgomery PA-
508 AM EDT Sat May 31 2025

...FLASH FLOOD WARNING WILL EXPIRE AT 515 AM EDT EARLY THIS MORNING 
FOR EASTERN BERKS, SOUTHERN LEHIGH, WEST CENTRAL BUCKS AND 
NORTHWESTERN MONTGOMERY COUNTIES...

The heavy rain has ended. While the threat for widespread flooding 
has ended, some creeks and streams continue to slowly rise. More 
targeted flood warnings have been issued. Have a way to receive 
warnings and please continue to heed remaining road closures.

A Flood Watch remains in effect until 800 AM EDT for portions of 
northern Delaware and Pennsylvania.

&&

LAT...LON 4042 7605 4051 7598 4059 7596 4064 7558
      4061 7543 4057 7539 4040 7535 4014 7533
      4013 7549 4014 7551 4016 7550 4015 7552
      4020 7556 4024 7560 4022 7561 4024 7570
      4021 7575 4031 7601

$$

Hoeflich

The office that day

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

Issued	Product	Office	Counties	Lasted
May 30, 11:12 PM EDT	Flash Flood Warning	PHI	Chester, Delaware	3 hr
May 30, 11:36 PM EDT	Flash Flood Warning	PHI	Bucks, Chester, Delaware, Montgomery, Philadelphia	4 hr
May 31, 12:34 AM EDT	Flash Flood Warning	PHI	Bucks	3 hr
May 31, 5:06 AM EDT	Areal Flood Warning	PHI	Lehigh, Montgomery	5 hr
May 31, 8:42 AM EDT	Areal Flood Warning	PHI	Lehigh	4 hr

Nearby

Flash Flood Warnings in Pennsylvania, 2025 Every flash flood warning in 2025

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.