Right now
The most recent data we hold from NOAA arrived 57 minutes 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 20:45 UTC. It is kept here as a record.
It is the 4th strongest of the 97 detections recorded within 20 km of this point since 16 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 3:57PM EDT until May 20 at 4:45PM EDT by NWS Mount Holly NJ
An estimated 277,482 people live within 50 km of this point.
Nearby, since 16 March 2026
- August 7, 2026 · score 37 · 5.7 km
- March 17, 2026 · score 43 · 6.2 km
- July 9, 2026 · score 43 · 11.5 km
How we know
One source: NOAA. Not yet confirmed by a second, independent source.
Our own score for this event is 43 out of 100, at 80 % 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) | 43 / 100 |
| Our confidence | 80% |
| Coordinates | 39.9128, -76.7584 |
| Nearest City | York (6 km) |
| Population Exposed | 277.5K within 50 km |
| Impact Tier | significant |
| Timestamp | 2026-05-20T19:57:00.000Z |
| Source | https://api.weather.gov/alerts/merged_Severe Thunderstorm Warning_noaa_urn:oid:2.49.0.1.840.0.d49ee16cc91daba4dfb9b456f5dfc80d |
Score Breakdown
Technical Details
| Event | Severe Thunderstorm Warning |
| Urgency | Immediate |
| Certainty | Observed |
| AreaDesc | Berks, PA; Lehigh, PA; Carroll, MD; Frederick, MD; Lancaster, PA; York, PA and 2 more areas |
| Headline | Severe Thunderstorm Warning issued May 20 at 3:57PM EDT until May 20 at 4:45PM EDT by NWS Mount Holly NJ |
| Expires | 2026-05-20T16:45:00-04:00 |
| SenderName | NWS Mount Holly NJ |
| HasExactCoords | true |
| MergedCount | 5 |
| MergedIds | ["noaa_urn:oid:2.49.0.1.840.0.d49ee16cc91daba4dfb9b456f5dfc80d38a1bc2a.001.1","noaa_urn:oid:2.49.0.1.840.0.0ffe476efd628c87f990033aee2183a186286278.001.1","noaa_urn:oid:2.49.0.1.840.0.5ed1aff7c835f2ae9a3254701b57db7e124869e0.001.1","noaa_urn:oid:2.49.0.1.840.0.b6dd6edc202b43936fad86731e9dae1a2ed34101.001.1","noaa_urn:oid:2.49.0.1.840.0.55ce805d4e6d30164e3c1dbd85356d0d8e94943e.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 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.
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