This alert expired on 11 August 2026 at 04:04 UTC. It is kept here as a record.
No stronger detection stands among the 51 recorded within 20 km of this point since 22 March 2026 — 4 others scored the same. Another comparable one was recorded here earlier the same day. 12 more were recorded here in the fortnight before it.
What the source measured
NOAA reported: Tornado Warning issued August 10 at 9:54PM MDT until August 10 at 10:00PM MDT by NWS Rapid City SD
How we know
Confirmed by 4 independent sources, including NOAA.
Our own score for this event is 46 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 | critical |
| Calamity Score (ours) | 46 / 100 |
| Our confidence | 70% |
| Coordinates | 44.6760, -101.9200 |
| Nearest City | Rapid City (123 km) |
| Impact Tier | minor |
| Timestamp | 2026-08-11T03:54:00.000Z |
Score Breakdown
Technical Details
| Event | Tornado Warning |
| Urgency | Immediate |
| Certainty | Observed |
| AreaDesc | Ziebach, SD |
| Headline | Tornado Warning issued August 10 at 9:54PM MDT until August 10 at 10:00PM MDT by NWS Rapid City SD |
| Expires | 2026-08-10T22:04:00-06:00 |
| SenderName | NWS Rapid City SD |
| HasExactCoords | true |
| Iem TypeSummary | C |
| Iem City | 9 SSW Usta |
| Iem County | Perkins |
| Iem State | SD |
| Iem Wfo | UNR |
| Iem Remark | Ongoing. |
| MergedSources | [{"id":"iem_T_44.920_-102.120_1786418220000","source":"iem","severity":"low","severityValue":25,"timestamp":1786418220000,"latitude":44.92,"longitude":-102.12},{"id":"iem_C_45.270_-102.330_1786415160000","source":"iem","severity":"low","severityValue":25,"timestamp":1786415160000,"latitude":45.27,"longitude":-102.33},{"id":"iem_C_45.110_-102.260_1786416600000","source":"iem","severity":"low","severityValue":25,"timestamp":1786416600000,"latitude":45.11,"longitude":-102.26}] |
Safety Information
If a tornado warning is issued: go to a basement or an interior room on the lowest floor, away from windows. A vehicle and a mobile home are not shelter. Cover your head and neck. Wait for the official all-clear before going outside, and watch for downed power lines and gas leaks afterwards.
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.
Calamity.live data shows a weather event with CalamityScore 46/100, near Rapid City (United States), based on data from noaa. Source: Calamity.live, a platform aggregating real-time data from 191 scientific monitoring sources.