Right now
The most recent data we hold from NOAA arrived 68 minutes ago, and this point is not in it. We record detections, not passes: an absence is not proof that nothing is there.
Nothing else has been detected within 20 km in the last 24 hours.
This alert expired on 17 May 2026 at 21:15 UTC. It is kept here as a record.
It is the 10th strongest of the 67 detections recorded within 20 km of this point since 13 April 2026. Another comparable one was recorded here earlier the same day. 11 more were recorded here in the fortnight before it.
What the source measured
NOAA reported: Tornado Warning issued May 17 at 3:50PM CDT until May 17 at 4:15PM CDT by NWS Sioux Falls SD
How we know
Confirmed by 8 independent sources, including NOAA.
Our own score for this event is 46 out of 100, at 69 % confidence.
The score is ours, computed from intensity, exposed population and local history — not the source’s.
Computed under scoring rules v1. Rows carrying other versions were judged by different rules and are not directly comparable.
Event Data
| Type | Severe Weather |
| Severity | Critical |
| Calamity Score (ours) | 46 / 100 |
| Our confidence | 69% |
| Coordinates | 43.1840, -97.2300 |
| Nearest City | Sioux Falls (57 km) |
| Impact Tier | minor |
| Timestamp | 2026-05-17T20:50:00.000Z |
| Source | https://api.weather.gov/alerts/urn:oid:2.49.0.1.840.0.30653ff43026bd428fc1d1eb37fb1dc76caa3e6c.002.1 |
Score Breakdown
Technical Details
| Event | Tornado Warning |
| Urgency | Immediate |
| Certainty | Observed |
| AreaDesc | Turner, SD; Yankton, SD |
| Headline | Tornado Warning issued May 17 at 3:50PM CDT until May 17 at 4:15PM CDT by NWS Sioux Falls SD |
| Expires | 2026-05-17T16:15:00-05:00 |
| SenderName | NWS Sioux Falls SD |
| HasExactCoords | true |
| Iem TypeSummary | D |
| Iem City | 2 W Avon |
| Iem County | Bon Homme |
| Iem State | SD |
| Iem Wfo | FSD |
| Iem Remark | Trained spotter reported a shed with its roof blown off. |
| MergedSources | [{"id":"iem_G_43.010_-98.000_1779047880000","source":"iem","severity":"low","severityValue":25,"timestamp":1779047880000,"latitude":43.01,"longitude":-98},{"id":"iem_D_43.160_-97.970_1779048300000","source":"iem","severity":"low","severityValue":25,"timestamp":1779048300000,"latitude":43.16,"longitude":-97.97},{"id":"iem_G_43.000_-97.970_1779048000000","source":"iem","severity":"low","severityValue":25,"timestamp":1779048000000,"latitude":43,"longitude":-97.97},{"id":"iem_G_43.080_-98.130_1779047520000","source":"iem","severity":"low","severityValue":25,"timestamp":1779047520000,"latitude":43.08,"longitude":-98.13},{"id":"iem_H_43.220_-97.510_1779050640000","source":"iem","severity":"low","severityValue":25,"timestamp":1779050640000,"latitude":43.22,"longitude":-97.51},{"id":"iem_G_43.160_-97.760_1779048960000","source":"iem","severity":"low","severityValue":25,"timestamp":1779048960000,"latitude":43.16,"longitude":-97.76},{"id":"iem_D_43.010_-98.100_1779047640000","source":"iem","severity":"low","severityValue":25,"timestamp":1779047640000,"latitude":43.01,"longitude":-98.1}] |
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 8 March 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 46/100 (United States), based on data from noaa. Source: Calamity.live, a platform aggregating real-time data from 185 scientific monitoring sources.