Right now
The most recent data we hold from NOAA arrived 2 hours ago, and this point is not in it. We record detections, not passes: an absence is not proof that nothing is there.
Nothing else has been detected within 20 km in the last 24 hours.
This alert expired on 20 May 2026 at 22:00 UTC. It is kept here as a record.
It is the 7th strongest of the 277 detections recorded within 20 km of this point since 17 March 2026. Another comparable one was recorded here earlier the same day. 5 more were recorded here in the fortnight before it.
What the source measured
NOAA reported: Severe Thunderstorm Warning issued May 20 at 5:15PM EDT until May 20 at 6:00PM EDT by NWS Mount Holly NJ
An estimated 2,946,741 people live within 50 km of this point.
Nearby, since 17 March 2026
- September 2, 2026 · score 46 · 5.2 km
- June 12, 2026 · score 46 · 5.6 km
- September 3, 2026 · score 46 · 7.6 km
How we know
Confirmed by 16 independent sources, including NOAA.
Our own score for this event is 52 out of 100, at 90 % confidence.
The score is ours, computed from intensity, exposed population and local history — not the source’s.
Computed under scoring rules v1. Rows carrying other versions were judged by different rules and are not directly comparable.
Event Data
| Type | Severe Weather |
| Severity | Medium |
| Calamity Score (ours) | 52 / 100 |
| Our confidence | 90% |
| Coordinates | 39.9895, -75.6704 |
| Nearest City | West Chester (6 km) |
| Population Exposed | 2.9M within 50 km |
| Impact Tier | significant |
| Timestamp | 2026-05-20T21:15:00.000Z |
| Source | https://api.weather.gov/alerts/merged_Severe Thunderstorm Warning_noaa_urn:oid:2.49.0.1.840.0.a79fcbad9fe48cd517cd5b3c7257b85d |
Score Breakdown
Technical Details
| Event | Severe Thunderstorm Warning |
| Urgency | Immediate |
| Certainty | Observed |
| AreaDesc | Burlington, NJ; Hunterdon, NJ; Mercer, NJ; Somerset, NJ; Bucks, PA; Chester, PA; Montgomery, PA; Philadelphia, PA; Camden, NJ; Gloucester, NJ; Chester, PA; Delaware, PA; Montgomery, PA; Philadelphia, PA; Baltimore, MD; Cecil, MD; Harford, MD and 3 more areas |
| Headline | Severe Thunderstorm Warning issued May 20 at 5:15PM EDT until May 20 at 6:00PM EDT by NWS Mount Holly NJ |
| Expires | 2026-05-20T18:00:00-04:00 |
| SenderName | NWS Mount Holly NJ |
| HasExactCoords | true |
| MergedCount | 7 |
| MergedIds | ["noaa_urn:oid:2.49.0.1.840.0.a79fcbad9fe48cd517cd5b3c7257b85d681c3c22.001.1","noaa_urn:oid:2.49.0.1.840.0.add74f0042af4b0db11f1149a47be98019241dbc.001.1","noaa_urn:oid:2.49.0.1.840.0.03418dc396e4d3faf052d15b003ce2ecdeba353f.001.1","noaa_urn:oid:2.49.0.1.840.0.bba37fed67e70fe0a935476932b2e196205c94be.001.1","noaa_urn:oid:2.49.0.1.840.0.5327e847d8dc69759689dde406184adf82605623.002.1","noaa_urn:oid:2.49.0.1.840.0.b4adbaf2e5bda1ffed8f8e512b361ece05f0d5a6.001.1","noaa_urn:oid:2.49.0.1.840.0.7772b2ba4415975e274f81ed1f32cef938c13d4b.001.1"] |
| Iem TypeSummary | D |
| Iem City | 3 WNW Robeson Twp |
| Iem County | Berks |
| Iem State | PA |
| Iem Wfo | PHI |
| Iem Remark | Tree down into a house. Time estimated from radar. |
| MergedSources | [{"id":"iem_D_40.540_-75.760_1779309180000","source":"iem","severity":"low","severityValue":25,"timestamp":1779309180000,"latitude":40.54,"longitude":-75.76},{"id":"iem_D_40.040_-76.360_1779306780000","source":"iem","severity":"low","severityValue":25,"timestamp":1779306780000,"latitude":40.04,"longitude":-76.36},{"id":"iem_D_39.950_-76.500_1779306960000","source":"iem","severity":"low","severityValue":25,"timestamp":1779306960000,"latitude":39.95,"longitude":-76.5},{"id":"iem_D_40.550_-76.000_1779308100000","source":"iem","severity":"low","severityValue":25,"timestamp":1779308100000,"latitude":40.55,"longitude":-76},{"id":"iem_D_40.330_-76.350_1779305700000","source":"iem","severity":"low","severityValue":25,"timestamp":1779305700000,"latitude":40.33,"longitude":-76.35},{"id":"iem_D_39.970_-76.490_1779307320000","source":"iem","severity":"low","severityValue":25,"timestamp":1779307320000,"latitude":39.97,"longitude":-76.49},{"id":"iem_D_40.250_-75.650_1779310080000","source":"iem","severity":"low","severityValue":25,"timestamp":1779310080000,"latitude":40.25,"longitude":-75.65},{"id":"iem_D_40.270_-75.820_1779309000000","source":"iem","severity":"low","severityValue":25,"timestamp":1779309000000,"latitude":40.27,"longitude":-75.82},{"id":"iem_D_40.020_-76.360_1779308040000","source":"iem","severity":"low","severityValue":25,"timestamp":1779308040000,"latitude":40.02,"longitude":-76.36},{"id":"iem_D_40.270_-75.930_1779308100000","source":"iem","severity":"low","severityValue":25,"timestamp":1779308100000,"latitude":40.27,"longitude":-75.93},{"id":"iem_D_40.300_-75.660_1779310020000","source":"iem","severity":"low","severityValue":25,"timestamp":1779310020000,"latitude":40.3,"longitude":-75.66},{"id":"iem_D_40.500_-75.880_1779308820000","source":"iem","severity":"low","severityValue":25,"timestamp":1779308820000,"latitude":40.5,"longitude":-75.88},{"id":"iem_D_40.060_-76.300_1779307020000","source":"iem","severity":"low","severityValue":25,"timestamp":1779307020000,"latitude":40.06,"longitude":-76.3},{"id":"iem_D_40.060_-76.290_1779306960000","source":"iem","severity":"low","severityValue":25,"timestamp":1779306960000,"latitude":40.06,"longitude":-76.29},{"id":"iem_D_40.260_-75.930_1779308040000","source":"iem","severity":"low","severityValue":25,"timestamp":1779308040000,"latitude":40.26,"longitude":-75.93}] |
Safety Information
Always follow official guidance from your local emergency management agency. This platform provides scientific monitoring data and is not a substitute for official warnings. If you are in immediate danger, contact your local emergency number.
Series begins 8 March 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 West Chester?