This alert expired on 11 August 2026 at 10:00 UTC. It is kept here as a record.
No stronger detection stands among the 43 recorded within 20 km of this point since 15 March 2026 — 18 others scored the same. Another comparable one was recorded here earlier the same day. 7 more were recorded here in the fortnight before it.
What the source measured
NOAA reported: Severe Thunderstorm Warning issued August 11 at 4:41AM CDT until August 11 at 5:00AM CDT by NWS Sioux Falls SD
An estimated 171,544 people live within 50 km of this point.
Nearby, since 15 March 2026
- July 26, 2026 · score 43 · 8.6 km
- June 28, 2026 · score 43 · 17.7 km
- July 2, 2026 · score 22 · 22.2 km
How we know
One source: NOAA. Not yet confirmed by a second, independent source.
Our own score for this event is 43 out of 100, at 81 % confidence.
The score is ours, computed from intensity, exposed population and local history — not the source’s.
Event Data
| Type | Severe weather |
| Severity | medium |
| Calamity Score (ours) | 43 / 100 |
| Our confidence | 81% |
| Coordinates | 43.2520, -96.5320 |
| Nearest City | Sioux Falls (36 km) |
| Population Exposed | 171.5K within 50 km |
| Impact Tier | significant |
| Timestamp | 2026-08-11T09:41:00.000Z |
| Source | https://api.weather.gov/alerts/urn:oid:2.49.0.1.840.0.805a6d809f571deaf85dcdaa6bbba551c86c546b.001.1 |
Score Breakdown
Technical Details
| Event | Severe Thunderstorm Warning |
| Urgency | Immediate |
| Certainty | Observed |
| AreaDesc | Lyon, IA; Sioux, IA; Lincoln, SD |
| Headline | Severe Thunderstorm Warning issued August 11 at 4:41AM CDT until August 11 at 5:00AM CDT by NWS Sioux Falls SD |
| Expires | 2026-08-11T05:00:00-05:00 |
| SenderName | NWS Sioux Falls SD |
| HasExactCoords | true |
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 43/100 (United States), based on data from noaa. Source: Calamity.live, a platform aggregating real-time data from 185 scientific monitoring sources.