Right now
The most recent data we hold from NOAA arrived 49 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 21:15 UTC. It is kept here as a record.
It is the 14th strongest of the 65 detections recorded within 20 km of this point since 17 March 2026. Another comparable one was recorded here earlier the same day. 10 more were recorded here in the fortnight before it.
What the source measured
NOAA reported: Severe Thunderstorm Warning issued May 20 at 4:29PM EDT until May 20 at 5:15PM EDT by NWS Mount Holly NJ
An estimated 384,416 people live within 50 km of this point.
Nearby, since 17 March 2026
- September 2, 2026 · score 37 · 7.8 km
- July 5, 2026 · score 48 · 8.1 km
- May 20, 2026 · score 48 · 8.3 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 79 % 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 | 79% |
| Coordinates | 39.8559, -76.4635 |
| Nearest City | Lancaster (24 km) |
| Population Exposed | 384.4K within 50 km |
| Impact Tier | significant |
| Timestamp | 2026-05-20T20:29:00.000Z |
| Source | https://api.weather.gov/alerts/merged_Severe Thunderstorm Warning_noaa_urn:oid:2.49.0.1.840.0.0ab05cd5869e39cbee5a9f29a40a3594 |
Score Breakdown
Technical Details
| Event | Severe Thunderstorm Warning |
| Urgency | Immediate |
| Certainty | Observed |
| AreaDesc | Berks, PA; Chester, PA; Montgomery, PA; Berks, PA; Lehigh, PA; Lancaster, PA and 4 more areas |
| Headline | Severe Thunderstorm Warning issued May 20 at 4:29PM EDT until May 20 at 5:15PM EDT by NWS Mount Holly NJ |
| Expires | 2026-05-20T17:15:00-04:00 |
| SenderName | NWS Mount Holly NJ |
| HasExactCoords | true |
| MergedCount | 8 |
| MergedIds | ["noaa_urn:oid:2.49.0.1.840.0.0ab05cd5869e39cbee5a9f29a40a3594d4db6a06.001.1","noaa_urn:oid:2.49.0.1.840.0.53946a10d5ab41fce2586b92cdf04eaf2e0d692b.001.1","noaa_urn:oid:2.49.0.1.840.0.a8bdf41eb46defff1c2c8b77ddb6618195a4c8a7.001.1","noaa_urn:oid:2.49.0.1.840.0.2469b311e4f66eb731f22833246ed389f1412280.002.1","noaa_urn:oid:2.49.0.1.840.0.1c8e99e1bbee2af388c0600d82a297b2998ee31a.001.1","noaa_urn:oid:2.49.0.1.840.0.a0ab8246b7b09ef29b85c3ecf668bffad604ded6.001.1","noaa_urn:oid:2.49.0.1.840.0.467ed2667cb19e1e8a04b08c7618f3c53e6b4665.001.1","noaa_urn:oid:2.49.0.1.840.0.51f9274d2e052b1aaa3e081af95b1bac4256833e.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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