Right now
The most recent data we hold from NOAA arrived 6 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 22:15 UTC. It is kept here as a record.
No stronger detection stands among the 66 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. 10 more were recorded here in the fortnight before it.
What the source measured
NOAA reported: Tornado Warning issued May 17 at 5:01PM CDT until May 17 at 5:15PM CDT by NWS Sioux Falls SD
Urban PEI: 171,544 within a heuristic 50 km radius; not unique people.
Nearby, since 15 March 2026
- May 17, 2026 · score 67 · 0.0 km
- July 26, 2026 · score 43 · 16.5 km
- May 25, 2026 · score 43 · 16.7 km
How we know
10 recorded sources include NOAA; independence is not established by this count.
Our own score for this event is 67 out of 100.
This is our versioned heuristic index, not source severity or a calibrated probability. Urban PEI does not count unique people.
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) | 67 / 100 |
| Legacy data-support index | 0.89/1 |
| Coordinates | 43.4760, -96.5220 |
| Nearest City | Sioux Falls (18 km) |
| Urban exposure index (PEI) | 171.5K within 50 km |
| Impact Tier | severe |
| Timestamp | 2026-05-17T22:01:00.000Z |
| Source | https://api.weather.gov/alerts/urn:oid:2.49.0.1.840.0.d88de60d90d758b2571ce1eaf8ea5e8950dba598.002.1 |
Physical priority index · v1. Heuristic priority, not calibrated probability, predictive accuracy or damage. The legacy data-support index combines assigned source support and field availability. Urban PEI is distance-weighted and does not count unique people; zero does not establish that nobody is present. Model cards.
Source and revision timeline
Source: noaa. Occurrence: 2026-05-17T22:01:00.000Z.
First archived: 2026-05-17T22:08:28.610Z. Material modification: not recorded.
Retained revisions are prospective; earlier versions may be unavailable. No revision entry does not prove that a record never changed.
Score Breakdown
Technical Details
| Event | Tornado Warning |
| Urgency | Immediate |
| Certainty | Observed |
| AreaDesc | Lyon, IA; Minnehaha, SD |
| Headline | Tornado Warning issued May 17 at 5:01PM CDT until May 17 at 5:15PM CDT by NWS Sioux Falls SD |
| Expires | 2026-05-17T17:15:00-05:00 |
| 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 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.
Review the area, threshold and delivery channel in your account.
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