This alert expired on 17 May 2026 at 22:18 UTC. It is kept here as a record.
No stronger detection stands among the 65 recorded within 20 km of this point since 15 March 2026 — 3 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 May 17 at 5:08PM CDT until May 17 at 5:15PM 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 · 16.5 km
- May 25, 2026 · score 43 · 16.7 km
- June 18, 2026 · score 43 · 18.8 km
How we know
Confirmed by 10 independent sources, including NOAA.
Our own score for this event is 67 out of 100, at 89 % 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) | 67 / 100 |
| Our confidence | 89% |
| Coordinates | 43.4760, -96.5220 |
| Nearest City | Sioux Falls (18 km) |
| Population Exposed | 171.5K within 50 km |
| Impact Tier | severe |
| Timestamp | 2026-05-17T22:08:00.000Z |
| Source | https://api.weather.gov/alerts/urn:oid:2.49.0.1.840.0.611d057dfe6506bc50f33f5eca5789700e26082b.001.1 |
Score Breakdown
Technical Details
| Event | Tornado Warning |
| Urgency | Immediate |
| Certainty | Observed |
| AreaDesc | Lyon, IA; Minnehaha, SD |
| Headline | Tornado Warning issued May 17 at 5:08PM CDT until May 17 at 5:15PM CDT by NWS Sioux Falls SD |
| Expires | 2026-05-17T17:18:00-05:00 |
| SenderName | NWS Sioux Falls SD |
| HasExactCoords | true |
| Iem TypeSummary | G |
| Iem Magnitude | 70 |
| Iem Unit | MPH |
| Iem City | 2 ENE Chancellor |
| Iem County | Turner |
| Iem State | SD |
| Iem Wfo | FSD |
| Iem Remark | Via personal weather station. Exact time estimated via radar. |
| MergedSources | [{"id":"iem_H_43.180_-97.340_1779050640000","source":"iem","severity":"low","severityValue":25,"timestamp":1779050640000,"latitude":43.18,"longitude":-97.34},{"id":"iem_H_43.350_-96.930_1779052620000","source":"iem","severity":"low","severityValue":25,"timestamp":1779052620000,"latitude":43.35,"longitude":-96.93},{"id":"iem_H_43.480_-96.750_1779053760000","source":"iem","severity":"low","severityValue":25,"timestamp":1779053760000,"latitude":43.48,"longitude":-96.75},{"id":"iem_H_43.450_-96.840_1779053880000","source":"iem","severity":"low","severityValue":25,"timestamp":1779053880000,"latitude":43.45,"longitude":-96.84},{"id":"iem_G_43.260_-97.270_1779050820000","source":"iem","severity":"low","severityValue":25,"timestamp":1779050820000,"latitude":43.26,"longitude":-97.27},{"id":"iem_H_43.530_-96.840_1779053520000","source":"iem","severity":"low","severityValue":25,"timestamp":1779053520000,"latitude":43.53,"longitude":-96.84},{"id":"iem_H_43.490_-96.710_1779054420000","source":"iem","severity":"low","severityValue":25,"timestamp":1779054420000,"latitude":43.49,"longitude":-96.71},{"id":"iem_G_43.360_-96.990_1779052440000","source":"iem","severity":"low","severityValue":25,"timestamp":1779052440000,"latitude":43.36,"longitude":-96.99},{"id":"iem_G_43.390_-96.940_1779052620000","source":"iem","severity":"low","severityValue":25,"timestamp":1779052620000,"latitude":43.39,"longitude":-96.94}] |
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.
Want to know when something happens near Sioux Falls?
Calamity.live data shows a weather event with CalamityScore 67/100, near Sioux Falls (United States), based on data from noaa. Source: Calamity.live, a platform aggregating real-time data from 185 scientific monitoring sources.