Right now
The most recent data we hold from NOAA arrived 44 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 23:45 UTC. It is kept here as a record.
It is the 3rd strongest of the 73 detections recorded within 20 km of this point since 15 March 2026. Another comparable one was recorded here earlier the same day. 2 more were recorded here in the fortnight before it.
What the source measured
NOAA reported: Severe Thunderstorm Warning issued May 17 at 6:08PM CDT until May 17 at 6:45PM CDT by NWS Sioux Falls SD
Nearby, since 15 March 2026
- September 2, 2026 · score 46 · 14.4 km
How we know
9 recorded sources include NOAA; independence is not established by this count.
Our own score for this event is 22 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 | Medium |
| Calamity Score (ours) | 22 / 100 |
| Legacy data-support index | 0.69/1 |
| Coordinates | 43.4049, -95.9938 |
| Nearest City | Sioux Falls (61 km) |
| Urban exposure index (PEI) | 0 within 50 km |
| Impact Tier | minor |
| Timestamp | 2026-05-17T23:08:00.000Z |
| Source | https://api.weather.gov/alerts/merged_Severe Thunderstorm Warning_noaa_urn:oid:2.49.0.1.840.0.5c67a7ff8b2b6ead6c6014620690fe16 |
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: 2026-05-17T23:08:00.000Z.
First archived: 2026-05-17T23:15:15.377Z. 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 | Severe Thunderstorm Warning |
| Urgency | Immediate |
| Certainty | Observed |
| AreaDesc | Lyon, IA; Osceola, IA; Murray, MN; Nobles, MN; Lyon, IA; O'Brien, IA; Osceola, IA; Sioux, IA |
| Headline | Severe Thunderstorm Warning issued May 17 at 6:08PM CDT until May 17 at 6:45PM CDT by NWS Sioux Falls SD |
| Expires | 2026-05-17T18:45:00-05:00 |
| SenderName | NWS Sioux Falls SD |
| HasExactCoords | true |
| MergedCount | 2 |
| MergedIds | ["noaa_urn:oid:2.49.0.1.840.0.5c67a7ff8b2b6ead6c6014620690fe1647f57ee3.002.1","noaa_urn:oid:2.49.0.1.840.0.c618e55150d47ab87b3a230964891b1acccc5fba.001.1"] |
| Iem TypeSummary | H |
| Iem Magnitude | 1 |
| Iem Unit | Inch |
| Iem City | Valley Springs |
| Iem County | Minnehaha |
| Iem State | SD |
| Iem Wfo | FSD |
| MergedSources | [{"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_43.610_-96.380_1779056280000","source":"iem","severity":"low","severityValue":25,"timestamp":1779056280000,"latitude":43.61,"longitude":-96.38},{"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_43.620_-96.220_1779056760000","source":"iem","severity":"low","severityValue":25,"timestamp":1779056760000,"latitude":43.62,"longitude":-96.22},{"id":"iem_H_43.600_-96.090_1779057360000","source":"iem","severity":"low","severityValue":25,"timestamp":1779057360000,"latitude":43.6,"longitude":-96.09},{"id":"iem_H_43.590_-96.460_1779055320000","source":"iem","severity":"low","severityValue":25,"timestamp":1779055320000,"latitude":43.59,"longitude":-96.46}] |
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 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.
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