This alert expired on 20 May 2026 at 22:15 UTC. It is kept here as a record.
It is the 2nd strongest of the 230 detections recorded within 20 km of this point since 12 March 2026. Another comparable one was recorded here earlier the same day. 6 more were recorded here in the fortnight before it.
What the source measured
NOAA reported: Severe Thunderstorm Warning issued May 20 at 5:21PM EDT until May 20 at 6:15PM EDT by NWS Baltimore MD/Washington DC
An estimated 2,456,822 people live within 50 km of this point.
Nearby, since 12 March 2026
- March 17, 2026 · score 52 · 7.7 km
- July 9, 2026 · score 48 · 8.3 km
- June 12, 2026 · score 46 · 9.6 km
How we know
Confirmed by 13 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.
Event Data
| Type | Severe weather |
| Severity | medium |
| Calamity Score (ours) | 52 / 100 |
| Our confidence | 90% |
| Coordinates | 39.8577, -75.7195 |
| Nearest City | West Chester (15 km) |
| Population Exposed | 2.5M within 50 km |
| Impact Tier | significant |
| Timestamp | 2026-05-20T21:21:00.000Z |
Score Breakdown
Technical Details
| Event | Severe Thunderstorm Warning |
| Urgency | Immediate |
| Certainty | Observed |
| AreaDesc | Cecil, MD; Kent, DE; New Castle, DE; Kent, MD; Queen Anne's, MD; New Castle, DE; Chester, PA; Delaware, PA and 5 more areas |
| Headline | Severe Thunderstorm Warning issued May 20 at 5:21PM EDT until May 20 at 6:15PM EDT by NWS Baltimore MD/Washington DC |
| Expires | 2026-05-20T18:15:00-04:00 |
| SenderName | NWS Baltimore MD/Washington DC |
| HasExactCoords | true |
| MergedCount | 9 |
| MergedIds | ["noaa_urn:oid:2.49.0.1.840.0.fe508ac293398ad240466709cc560c926f8ccaa3.001.1","noaa_urn:oid:2.49.0.1.840.0.769b014eafcd4f80ea87246012a3bda6c57f8b7c.001.1","noaa_urn:oid:2.49.0.1.840.0.e15a34933f2dfa2b59f81144bf5f6b71eccdc245.001.1","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"] |
| 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_40.040_-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_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 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.
Calamity.live data shows a weather event with CalamityScore 52/100, near West Chester (United States), based on data from noaa. Source: Calamity.live, a platform aggregating real-time data from 191 scientific monitoring sources.