This alert expired on 21 July 2026 at 20:30 UTC. It is kept here as a record.
It is the 106th strongest of the 139 detections recorded within 20 km of this point since 17 March 2026. The last comparable one was on 19 July 2026. 6 more were recorded here in the fortnight before it.
What the source measured
NOAA reported: Severe Thunderstorm Warning issued July 21 at 3:37PM EDT until July 21 at 4:30PM EDT by NWS Mount Holly NJ
An estimated 249,990 people live within 50 km of this point.
Nearby, since 17 March 2026
- June 22, 2026 · score 43 · 4.5 km
- June 22, 2026 · score 43 · 9.2 km
- July 4, 2026 · score 43 · 12.2 km
How we know
One source: NOAA. Not yet confirmed by a second, independent source.
Our own score for this event is 37 out of 100, at 79 % 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) | 37 / 100 |
| Our confidence | 79% |
| Coordinates | 40.1470, -75.9942 |
| Nearest City | Reading (22 km) |
| Population Exposed | 250.0K within 50 km |
| Impact Tier | significant |
| Timestamp | 2026-07-21T19:37:00.000Z |
Score Breakdown
Technical Details
| Event | Severe Thunderstorm Warning |
| Urgency | Immediate |
| Certainty | Observed |
| AreaDesc | Chester, PA; Delaware, PA; Schuylkill, PA; Lancaster, PA; York, PA |
| Headline | Severe Thunderstorm Warning issued July 21 at 3:37PM EDT until July 21 at 4:30PM EDT by NWS Mount Holly NJ |
| Expires | 2026-07-21T16:30:00-04:00 |
| SenderName | NWS Mount Holly NJ |
| HasExactCoords | true |
| MergedCount | 3 |
| MergedIds | ["noaa_urn:oid:2.49.0.1.840.0.477b922e914a231a5af6b5bfaba618244fc9c644.001.1","noaa_urn:oid:2.49.0.1.840.0.e85768ee45ac2aad87f555d8b6fd750c3fe2593b.001.1","noaa_urn:oid:2.49.0.1.840.0.aa1fcfd94557c7f36f94efcf47db15d046eebd94.001.1"] |
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 37/100, near Reading (United States), based on data from noaa. Source: Calamity.live, a platform aggregating real-time data from 191 scientific monitoring sources.