This alert expired on 2 September 2026 at 01:45 UTC. It is kept here as a record.
No stronger detection stands among the 135 recorded within 20 km of this point since 25 May 2026 — 101 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 8:26PM CDT until September 1 at 8:45PM CDT by NWS Sioux Falls SD
Nearby, since 25 May 2026
- July 3, 2026 · score 22 · 15.7 km
- May 25, 2026 · score 22 · 20.5 km
How we know
Confirmed by 3 independent sources, including NOAA.
Our own score for this event is 28 out of 100, at 71 % 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 | 71% |
| Coordinates | 42.6979, -97.6243 |
| Nearest City | Norfolk (76 km) |
| Impact Tier | minor |
| Timestamp | 2026-09-02T01:26:00.000Z |
| Source | https://api.weather.gov/alerts/urn%3Aoid%3A2.49.0.1.840.0.c9a4a2e180b38e06084f64a7bd2f26549e014c60.001.1 |
Score Breakdown
Technical Details
| Event | Severe Thunderstorm Warning |
| Urgency | Immediate |
| Certainty | Observed |
| AreaDesc | Bon Homme, SD; Yankton, SD; Bon Homme, SD; Clay, SD; Yankton, SD; Antelope, NE and 1 more areas |
| Headline | Severe Thunderstorm Warning issued September 1 at 8:26PM CDT until September 1 at 8:45PM CDT by NWS Sioux Falls SD |
| Expires | 2026-09-01T20:45:00-05:00 |
| SenderName | NWS Sioux Falls SD |
| HasExactCoords | true |
| MergedCount | 4 |
| MergedIds | ["noaa_urn:oid:2.49.0.1.840.0.c9a4a2e180b38e06084f64a7bd2f26549e014c60.001.1","noaa_urn:oid:2.49.0.1.840.0.750ac1825a955a7d58ac4f673630092848cda779.001.1","noaa_urn:oid:2.49.0.1.840.0.ecef515d3f76c9b525dd3df96112b617effde9e7.001.1","noaa_urn:oid:2.49.0.1.840.0.e6a7a41ccd597e6d12e2a3ad59e362d8263c75f2.001.1"] |
| Spc ReportType | hail |
| Spc Speed | 175 |
| Spc Location | Santee |
| Spc County | Knox |
| Spc State | NE |
| Spc Comments | Public report of various hail sizes with largest around golf ball size. Time estimated via radar. (OAX) |
| Iem TypeSummary | H |
| Iem Magnitude | 1 |
| Iem Unit | Inch |
| Iem City | 2 WSW Niobrara |
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.