This alert expired on 13 May 2026 at 21:00 UTC. It is kept here as a record.
No stronger detection stands among the 12 recorded within 20 km of this point since 24 April 2026 — 3 others scored the same. The last comparable one was on 24 April 2026.
What the source measured
NOAA reported: Severe Thunderstorm Warning issued May 13 at 2:13PM MDT until May 13 at 3:00PM MDT by NWS Great Falls MT
An estimated 66,281 people live within 50 km of this point.
Nearby, since 24 April 2026
- May 13, 2026 · score 34 · 16.5 km
- May 27, 2026 · score 39 · 17.6 km
How we know
Confirmed by 2 independent sources, including NOAA.
Our own score for this event is 39 out of 100, at 84 % 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) | 39 / 100 |
| Our confidence | 84% |
| Coordinates | 46.2407, -112.0750 |
| Nearest City | Helena (39 km) |
| Population Exposed | 66.3K within 50 km |
| Impact Tier | significant |
| Timestamp | 2026-05-13T20:13:00.000Z |
| Source | https://api.weather.gov/alerts/merged_Severe Thunderstorm Warning_noaa_urn:oid:2.49.0.1.840.0.ac23624f833cc79cc2fbe2219ba1be2e |
Score Breakdown
Technical Details
| Event | Severe Thunderstorm Warning |
| Urgency | Immediate |
| Certainty | Observed |
| AreaDesc | Beaverhead, MT; Madison, MT; Cascade, MT; Lewis and Clark, MT |
| Headline | Severe Thunderstorm Warning issued May 13 at 2:13PM MDT until May 13 at 3:00PM MDT by NWS Great Falls MT |
| Expires | 2026-05-13T15:00:00-06:00 |
| SenderName | NWS Great Falls MT |
| HasExactCoords | true |
| MergedCount | 2 |
| MergedIds | ["noaa_urn:oid:2.49.0.1.840.0.ac23624f833cc79cc2fbe2219ba1be2eed2e2ba3.001.1","noaa_urn:oid:2.49.0.1.840.0.df1d26b08779cca61cab508ced75f50c783a83ec.001.1"] |
| Iem TypeSummary | G |
| Iem Magnitude | 54 |
| Iem Unit | MPH |
| Iem City | 3 SSE Butte |
| Iem County | Silver Bow |
| Iem State | MT |
| Iem Wfo | MSO |
| Iem Remark | ASOS station KBTM Butte-mooney Ap. |
| MergedSources | [{"id":"iem_G_45.970_-112.500_1778701980000","source":"iem","severity":"low","severityValue":25,"timestamp":1778701980000,"latitude":45.97,"longitude":-112.5}] |
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 in this area?
Calamity.live data shows a weather event with CalamityScore 39/100 (United States), based on data from noaa. Source: Calamity.live, a platform aggregating real-time data from 185 scientific monitoring sources.