This alert expired on 30 May 2026 at 01:30 UTC. It is kept here as a record.
No stronger detection stands among the 20 recorded within 20 km of this point since 13 May 2026 — 13 others scored the same. 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 29 at 7:20PM MDT until May 29 at 7:30PM MDT by NWS Great Falls MT
Nearby, since 13 May 2026
- July 7, 2026 · score 16 · 10.6 km
- May 14, 2026 · score 22 · 11.0 km
- May 13, 2026 · score 22 · 13.5 km
How we know
Confirmed by 2 independent sources, including NOAA.
Our own score for this event is 22 out of 100, at 63 % 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) | 22 / 100 |
| Our confidence | 63% |
| Coordinates | 47.6014, -108.4695 |
| Nearest City | Billings (203 km) |
| Impact Tier | minor |
| Timestamp | 2026-05-30T01:20:00.000Z |
| Source | https://api.weather.gov/alerts/merged_Severe Thunderstorm Warning_noaa_urn:oid:2.49.0.1.840.0.757c40318006cdd0a25c17f72efb29c2 |
Score Breakdown
Technical Details
| Event | Severe Thunderstorm Warning |
| Urgency | Immediate |
| Certainty | Observed |
| AreaDesc | Fergus, MT; Garfield, MT; Petroleum, MT; Phillips, MT |
| Headline | Severe Thunderstorm Warning issued May 29 at 7:20PM MDT until May 29 at 7:30PM MDT by NWS Great Falls MT |
| Expires | 2026-05-29T19:30:00-06:00 |
| SenderName | NWS Great Falls MT |
| HasExactCoords | true |
| MergedCount | 2 |
| MergedIds | ["noaa_urn:oid:2.49.0.1.840.0.757c40318006cdd0a25c17f72efb29c22e47c6fb.001.1","noaa_urn:oid:2.49.0.1.840.0.ee62b7ac224718b75d1601c90fce06f45edb1a54.001.1"] |
| Iem TypeSummary | G |
| Iem Magnitude | 70 |
| Iem Unit | MPH |
| Iem City | 13 ENE Roy |
| Iem County | Fergus |
| Iem State | MT |
| Iem Wfo | TFX |
| MergedSources | [{"id":"iem_G_47.380_-108.680_1780101000000","source":"iem","severity":"low","severityValue":25,"timestamp":1780101000000,"latitude":47.38,"longitude":-108.68}] |
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 22/100 (United States), based on data from noaa. Source: Calamity.live, a platform aggregating real-time data from 185 scientific monitoring sources.