This alert expired on 2 September 2026 at 01:45 UTC. It is kept here as a record.
No stronger detection stands among the 48 recorded within 20 km of this point since 29 June 2026 — 32 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 7:53PM CDT until September 1 at 8:45PM CDT by NWS Sioux Falls SD
Nearby, since 29 June 2026
- June 29, 2026 · score 16 · 10.5 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 | 42.6136, -98.1484 |
| Nearest City | Norfolk (88 km) |
| Impact Tier | minor |
| Timestamp | 2026-09-02T00:53:00.000Z |
| Source | https://api.weather.gov/alerts/urn%3Aoid%3A2.49.0.1.840.0.ddd98b8533adeaf5eb08b0b5723c625ed3d3de71.001.1 |
Score Breakdown
Technical Details
| Event | Severe Thunderstorm Warning |
| Urgency | Immediate |
| Certainty | Observed |
| AreaDesc | Bon Homme, SD; Yankton, SD; Antelope, NE; Knox, NE; Holt, NE and 1 more areas |
| Headline | Severe Thunderstorm Warning issued September 1 at 7:53PM 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 | 6 |
| MergedIds | ["noaa_urn:oid:2.49.0.1.840.0.ddd98b8533adeaf5eb08b0b5723c625ed3d3de71.001.1","noaa_urn:oid:2.49.0.1.840.0.d2ddd97c49eabd265db50e112524803925b677c5.001.1","noaa_urn:oid:2.49.0.1.840.0.753016e28a36c1ca90c956406fd7ba4db0973a52.001.1","noaa_urn:oid:2.49.0.1.840.0.c54b273b3481f2c3da45d62c841ad9f733c19378.001.1","noaa_urn:oid:2.49.0.1.840.0.a930d4213241170bc3cba40e1d51d4171bdf30eb.002.1","noaa_urn:oid:2.49.0.1.840.0.b0a7009363c54481ad230b36ddb2d37b4184ae13.001.1"] |
| Spc ReportType | hail |
| Spc Speed | 125 |
| Spc Location | Niobrara |
| Spc County | Knox |
| Spc State | NE |
| Spc Comments | Report of quarters with half dollars at the corner of Walnut Street and Spruce Avenue. (OAX) |
| Iem TypeSummary | G |
| Iem Magnitude | 60 |
| Iem Unit | MPH |
| Iem City | 2 S Monowi |
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.