This alert expired on 2 September 2026 at 02:30 UTC. It is kept here as a record.
It is the 6th strongest of the 101 detections recorded within 20 km of this point since 16 March 2026. Another comparable one was recorded here earlier the same day.
What the source measured
NOAA reported: Severe Thunderstorm Warning issued September 1 at 9:15PM CDT until September 1 at 9:30PM CDT by NWS Sioux Falls SD
Nearby, since 16 March 2026
- July 3, 2026 · score 22 · 12.3 km
- September 2, 2026 · score 46 · 24.2 km
How we know
Confirmed by 3 independent sources, including NOAA.
Our own score for this event is 28 out of 100, at 72 % 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 | 72% |
| Coordinates | 42.6739, -97.3276 |
| Nearest City | Norfolk (72 km) |
| Impact Tier | minor |
| Timestamp | 2026-09-02T02:15:00.000Z |
| Source | https://api.weather.gov/alerts/urn%3Aoid%3A2.49.0.1.840.0.f129a91fa01a7e05464062ed8e496b32846f1002.002.1 |
Score Breakdown
Technical Details
| Event | Severe Thunderstorm Warning |
| Urgency | Immediate |
| Certainty | Observed |
| AreaDesc | Clay, SD; Union, SD; Antelope, NE; Pierce, NE; Clay, SD; Yankton, SD |
| Headline | Severe Thunderstorm Warning issued September 1 at 9:15PM CDT until September 1 at 9:30PM CDT by NWS Sioux Falls SD |
| Expires | 2026-09-01T21:30:00-05:00 |
| SenderName | NWS Sioux Falls SD |
| HasExactCoords | true |
| MergedCount | 3 |
| MergedIds | ["noaa_urn:oid:2.49.0.1.840.0.f129a91fa01a7e05464062ed8e496b32846f1002.002.1","noaa_urn:oid:2.49.0.1.840.0.32219594a52b2d7cfa8f27e81cfb9c261be08b85.001.1","noaa_urn:oid:2.49.0.1.840.0.2c1c127d7a0f6c4b6d8ecc3b5d38b424c94a8904.002.1"] |
| 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 | G |
| Iem Magnitude | 63 |
| Iem Unit | MPH |
| Iem City | 3 N Hartington |
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.