Right now
The most recent data we hold from NOAA arrived 7 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 20:15 UTC. It is kept here as a record.
It is the 10th strongest of the 168 detections recorded within 20 km of this point since 12 March 2026. Another comparable one was recorded here earlier the same day. 3 more were recorded here in the fortnight before it.
What the source measured
NOAA reported: Severe Thunderstorm Warning issued May 20 at 3:27PM EDT until May 20 at 4:15PM EDT by NWS State College PA
An estimated 506,141 people live within 50 km of this point.
Nearby, since 12 March 2026
- May 20, 2026 · score 48 · 4.7 km
- August 27, 2026 · score 43 · 6.0 km
- March 12, 2026 · score 48 · 7.4 km
How we know
Confirmed by 3 independent sources, including NOAA.
Our own score for this event is 48 out of 100, at 91 % 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) | 48 / 100 |
| Our confidence | 91% |
| Coordinates | 39.5353, -77.4039 |
| Nearest City | Frederick (14 km) |
| Population Exposed | 506.1K within 50 km |
| Impact Tier | significant |
| Timestamp | 2026-05-20T19:27:00.000Z |
| Source | https://api.weather.gov/alerts/merged_Severe Thunderstorm Warning_noaa_urn:oid:2.49.0.1.840.0.55ce805d4e6d30164e3c1dbd85356d0d |
Score Breakdown
Technical Details
| Event | Severe Thunderstorm Warning |
| Urgency | Immediate |
| Certainty | Observed |
| AreaDesc | Dauphin, PA; Lebanon, PA; Schuylkill, PA; Frederick, MD; Washington, MD; Loudoun, VA; Jefferson, WV; Clarke, VA; Frederick, VA; Warren, VA and 1 more areas |
| Headline | Severe Thunderstorm Warning issued May 20 at 3:27PM EDT until May 20 at 4:15PM EDT by NWS State College PA |
| Expires | 2026-05-20T16:15:00-04:00 |
| SenderName | NWS State College PA |
| HasExactCoords | true |
| MergedCount | 4 |
| MergedIds | ["noaa_urn:oid:2.49.0.1.840.0.55ce805d4e6d30164e3c1dbd85356d0d8e94943e.001.1","noaa_urn:oid:2.49.0.1.840.0.c83f1acf2d76de3614bce406b95f08d274f4e530.001.1","noaa_urn:oid:2.49.0.1.840.0.bd26181b2c0736ba4cbc43272ec8d47ccce4bbca.001.1","noaa_urn:oid:2.49.0.1.840.0.d8b5a2aaf5c67c4bac7271b6a01cd6c55b6ea231.001.1"] |
| Iem TypeSummary | D |
| Iem City | 4 WNW Greencastle |
| Iem County | Franklin |
| Iem State | PA |
| Iem Wfo | CTP |
| Iem Remark | Wires down reported in Upton along Lemar Road and Buchanan Trail West. |
| MergedSources | [{"id":"iem_D_39.760_-77.860_1779298500000","source":"iem","severity":"low","severityValue":25,"timestamp":1779298500000,"latitude":39.76,"longitude":-77.86},{"id":"iem_D_39.810_-77.810_1779298980000","source":"iem","severity":"low","severityValue":25,"timestamp":1779298980000,"latitude":39.81,"longitude":-77.81}] |
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 Frederick?
Calamity.live data shows a weather event with CalamityScore 48/100, near Frederick (United States), based on data from noaa. Source: Calamity.live, a platform aggregating real-time data from 185 scientific monitoring sources.