This alert expired on 1 September 2026 at 23:00 UTC. It is kept here as a record.
No stronger detection stands among the 74 recorded within 20 km of this point since 17 May 2026 — 52 others scored the same. Another comparable one was recorded here earlier the same day.
What the source measured
NOAA reported: Severe Thunderstorm Warning issued September 1 at 5:16PM CDT until September 1 at 6:00PM CDT by NWS Sioux Falls SD
Nearby, since 17 May 2026
- September 1, 2026 · score 28 · 19.2 km
How we know
Confirmed by 3 independent sources, including NOAA.
Our own score for this event is 28 out of 100, at 70 % confidence.
The score is ours, computed from intensity, exposed population and local history — not the source’s.
Event Data
| Type | Severe weather |
| Severity | high |
| Calamity Score (ours) | 28 / 100 |
| Our confidence | 70% |
| Coordinates | 42.9035, -98.8576 |
| Nearest City | Mitchell (112 km) |
| Impact Tier | minor |
| Timestamp | 2026-09-01T22:16:00.000Z |
| Source | https://api.weather.gov/alerts/urn%3Aoid%3A2.49.0.1.840.0.10342d4ead818d86a23431e4d0ec7ac617526677.001.1 |
Score Breakdown
Technical Details
| Event | Severe Thunderstorm Warning |
| Urgency | Immediate |
| Certainty | Observed |
| AreaDesc | Gregory, SD; Brown, NE; Rock, NE; Boyd, NE and 1 more areas |
| Headline | Severe Thunderstorm Warning issued September 1 at 5:16PM CDT until September 1 at 6:00PM CDT by NWS Sioux Falls SD |
| Expires | 2026-09-01T18:00:00-05:00 |
| SenderName | NWS Sioux Falls SD |
| HasExactCoords | true |
| MergedCount | 5 |
| MergedIds | ["noaa_urn:oid:2.49.0.1.840.0.10342d4ead818d86a23431e4d0ec7ac617526677.001.1","noaa_urn:oid:2.49.0.1.840.0.305af5b41331f5e336bbbf55eeda00066dd1144a.001.1","noaa_urn:oid:2.49.0.1.840.0.46cb337858ac7150aad404b2e0bab070ad352170.001.1","noaa_urn:oid:2.49.0.1.840.0.3b6ab2700c591f5c57805e66af0e81a8e3ac2b2f.001.1","noaa_urn:oid:2.49.0.1.840.0.b091d55a1d67e87fc228dfc2371a714ba2b62358.001.1"] |
| Spc ReportType | hail |
| Spc Speed | 100 |
| Spc Location | Fairfax |
| Spc County | Gregory |
| Spc State | SD |
| Spc Comments | Heavy rainfall accompanied mostly dime sized hail... but a few stones were as big as a quarter. (FSD) |
| Iem TypeSummary | H |
| Iem Magnitude | 1 |
| Iem Unit | Inch |
| Iem City | 3 ESE Naper |
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 10 February 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 28/100 (United States), based on data from noaa. Source: Calamity.live, a platform aggregating real-time data from 185 scientific monitoring sources.