This alert expired on 13 May 2026 at 21:51 UTC. It is kept here as a record.
It is the 4th strongest of the 9 detections recorded within 20 km of this point since 7 April 2026. Another comparable one was recorded here earlier the same day. 2 more were recorded here in the fortnight before it.
What the source measured
NOAA reported: Severe Thunderstorm Warning issued May 13 at 3:41PM MDT until May 13 at 3:45PM MDT by NWS Great Falls MT
An estimated 34,190 people live within 50 km of this point.
Nearby, since 7 April 2026
- May 13, 2026 · score 39 · 16.5 km
How we know
Confirmed by 6 independent sources, including NOAA.
Our own score for this event is 34 out of 100, at 90 % 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) | 34 / 100 |
| Our confidence | 90% |
| Coordinates | 46.1367, -111.9222 |
| Nearest City | Butte (49 km) |
| Population Exposed | 34.2K within 50 km |
| Impact Tier | significant |
| Timestamp | 2026-05-13T21:41:00.000Z |
| Source | https://api.weather.gov/alerts/urn:oid:2.49.0.1.840.0.55890c33725d993dbec90cb8f06d194629ebe64d.001.1 |
Score Breakdown
Technical Details
| Event | Severe Thunderstorm Warning |
| Urgency | Immediate |
| Certainty | Observed |
| AreaDesc | Broadwater, MT; Jefferson, MT |
| Headline | Severe Thunderstorm Warning issued May 13 at 3:41PM MDT until May 13 at 3:45PM MDT by NWS Great Falls MT |
| Expires | 2026-05-13T15:51:00-06:00 |
| SenderName | NWS Great Falls MT |
| HasExactCoords | true |
| Iem TypeSummary | G |
| Iem Magnitude | 62 |
| Iem Unit | MPH |
| Iem City | 2 ESE Twin Bridges |
| Iem County | Madison |
| Iem State | MT |
| Iem Wfo | TFX |
| Iem Remark | AWOS station KRVF 1 ESE Twin Bridges. |
| MergedSources | [{"id":"iem_N_45.500_-111.700_1778702400000","source":"iem","severity":"low","severityValue":25,"timestamp":1778702400000,"latitude":45.5,"longitude":-111.7},{"id":"iem_N_45.500_-111.700_1778698800000","source":"iem","severity":"low","severityValue":25,"timestamp":1778698800000,"latitude":45.5,"longitude":-111.7},{"id":"iem_N_45.500_-111.700_1778699700000","source":"iem","severity":"low","severityValue":25,"timestamp":1778699700000,"latitude":45.5,"longitude":-111.7},{"id":"iem_G_45.970_-112.500_1778701980000","source":"iem","severity":"low","severityValue":25,"timestamp":1778701980000,"latitude":45.97,"longitude":-112.5},{"id":"iem_G_45.530_-112.300_1778704500000","source":"iem","severity":"low","severityValue":25,"timestamp":1778704500000,"latitude":45.53,"longitude":-112.3}] |
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 34/100 (United States), based on data from noaa. Source: Calamity.live, a platform aggregating real-time data from 185 scientific monitoring sources.