This alert expired on 2 September 2026 at 02:45 UTC. It is kept here as a record.
It is the 199th strongest of the 263 detections recorded within 20 km of this point since 12 March 2026. Another comparable one was recorded here earlier the same day.
What the source measured
NOAA reported: Flash Flood Warning issued September 1 at 9:49PM EDT until September 1 at 10:45PM EDT by NWS Mount Holly NJ
An estimated 3,391,693 people live within 50 km of this point.
Nearby, since 12 March 2026
- July 9, 2026 · score 52 · 1.8 km
- May 20, 2026 · score 52 · 3.7 km
- August 28, 2026 · score 46 · 4.4 km
How we know
Confirmed by 3 independent sources, including NOAA.
Our own score for this event is 46 out of 100, at 92 % confidence.
The score is ours, computed from intensity, exposed population and local history — not the source’s.
Event Data
| Type | Severe weather |
| Severity | medium |
| Calamity Score (ours) | 46 / 100 |
| Our confidence | 92% |
| Coordinates | 40.0751, -75.4233 |
| Nearest City | King of Prussia (3 km) |
| Population Exposed | 3.4M within 50 km |
| Impact Tier | significant |
| Timestamp | 2026-09-02T01:49:00.000Z |
| Source | https://api.weather.gov/alerts/urn%3Aoid%3A2.49.0.1.840.0.d2671c54f2b35f20d213ebd305803986e2648aa6.001.1 |
Score Breakdown
Technical Details
| Event | Flash Flood Warning |
| Urgency | Immediate |
| Certainty | Likely |
| AreaDesc | Berks, PA; Atlantic, NJ; Camden, NJ; Gloucester, NJ; Hunterdon, NJ; Mercer, NJ; Middlesex, NJ; Bucks, PA and 1 more areas |
| Headline | Flash Flood Warning issued September 1 at 9:49PM EDT until September 1 at 10:45PM EDT by NWS Mount Holly NJ |
| Expires | 2026-09-01T22:45:00-04:00 |
| SenderName | NWS Mount Holly NJ |
| HasExactCoords | true |
| MergedCount | 4 |
| MergedIds | ["noaa_urn:oid:2.49.0.1.840.0.d2671c54f2b35f20d213ebd305803986e2648aa6.001.1","noaa_urn:oid:2.49.0.1.840.0.5ebe536de09e97831f4d52d9213353812270e84f.001.1","noaa_urn:oid:2.49.0.1.840.0.4ada0cfad29710623a8c48952a1539dbba0b9b22.001.1","noaa_urn:oid:2.49.0.1.840.0.c175b0136d66bbf500e095ab82f0d44ff4c26ef1.001.1"] |
| Spc ReportType | wind |
| Spc Speed | UNK |
| Spc Location | Mantua |
| Spc County | Gloucester |
| Spc State | NJ |
| Spc Comments | Fire Dept reports a tree into a house with 2 people trapped on Main Street in Mantua. No known injuries at time of report. (PHI) |
| Iem TypeSummary | D |
| Iem City | 2 NW Warwick Twp |
| Iem County | Chester |
| Iem State | PA |
Safety Information
During flooding: never walk, swim, or drive through floodwaters. Six inches of moving water can knock you down, and one foot of water can sweep away a vehicle. Move to higher ground if waters rise. After flooding, avoid contact with floodwater which may contain sewage, chemicals, or debris. Follow local emergency service guidance.
Series begins 10 February 2026. Comparisons refer to that period only. Collection gap: 14-26 August 2026.
This data is aggregated algorithmically from scientific sources. Not a replacement for official emergency warnings.
Want to know when something happens near King of Prussia?
Calamity.live data shows a weather event with CalamityScore 46/100, near King of Prussia (United States), based on data from noaa. Source: Calamity.live, a platform aggregating real-time data from 185 scientific monitoring sources.