Right now
The most recent data we hold from NOAA arrived 1 minute 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 18 May 2026 at 04:15 UTC. It is kept here as a record.
It is the 2nd strongest of the 54 detections recorded within 20 km of this point since 16 March 2026. The last comparable one was on 17 May 2026. 2 more were recorded here in the fortnight before it.
What the source measured
NOAA reported: Flash Flood Warning issued May 17 at 8:03PM CDT until May 17 at 11:15PM CDT by NWS Sioux Falls SD
An estimated 82,821 people live within 50 km of this point.
How we know
Confirmed by 15 independent sources, including NOAA.
Our own score for this event is 39 out of 100, at 90 % 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 | Medium |
| Calamity Score (ours) | 39 / 100 |
| Our confidence | 90% |
| Coordinates | 42.8820, -96.1750 |
| Nearest City | Sioux City (46 km) |
| Population Exposed | 82.8K within 50 km |
| Impact Tier | significant |
| Timestamp | 2026-05-18T01:03:00.000Z |
| Source | https://api.weather.gov/alerts/urn:oid:2.49.0.1.840.0.650cbd3752d3e430e75d3194482c2df797cb28e4.001.1 |
Score Breakdown
Technical Details
| Event | Flash Flood Warning |
| Urgency | Immediate |
| Certainty | Likely |
| AreaDesc | Plymouth, IA; Sioux, IA |
| Headline | Flash Flood Warning issued May 17 at 8:03PM CDT until May 17 at 11:15PM CDT by NWS Sioux Falls SD |
| Expires | 2026-05-17T23:15:00-05:00 |
| SenderName | NWS Sioux Falls SD |
| HasExactCoords | true |
| Iem TypeSummary | H |
| Iem Magnitude | 1.25 |
| Iem Unit | Inch |
| Iem City | Craig |
| Iem County | Plymouth |
| Iem State | IA |
| Iem Wfo | FSD |
| Iem Remark | Photo via social media. Time estimated by radar. |
| MergedSources | [{"id":"iem_G_42.460_-96.310_1779064560000","source":"iem","severity":"low","severityValue":25,"timestamp":1779064560000,"latitude":42.46,"longitude":-96.31},{"id":"iem_G_42.480_-96.190_1779065280000","source":"iem","severity":"low","severityValue":25,"timestamp":1779065280000,"latitude":42.48,"longitude":-96.19},{"id":"iem_T_42.630_-96.040_1779065820000","source":"iem","severity":"low","severityValue":25,"timestamp":1779065820000,"latitude":42.63,"longitude":-96.04},{"id":"iem_G_42.490_-96.060_1779065400000","source":"iem","severity":"low","severityValue":25,"timestamp":1779065400000,"latitude":42.49,"longitude":-96.06},{"id":"iem_H_43.410_-95.750_1779060960000","source":"iem","severity":"low","severityValue":25,"timestamp":1779060960000,"latitude":43.41,"longitude":-95.75},{"id":"iem_G_42.300_-96.320_1779064140000","source":"iem","severity":"low","severityValue":25,"timestamp":1779064140000,"latitude":42.3,"longitude":-96.32},{"id":"iem_G_42.530_-95.880_1779065820000","source":"iem","severity":"low","severityValue":25,"timestamp":1779065820000,"latitude":42.53,"longitude":-95.88},{"id":"iem_G_42.480_-95.860_1779065640000","source":"iem","severity":"low","severityValue":25,"timestamp":1779065640000,"latitude":42.48,"longitude":-95.86},{"id":"iem_G_42.520_-96.030_1779065760000","source":"iem","severity":"low","severityValue":25,"timestamp":1779065760000,"latitude":42.52,"longitude":-96.03},{"id":"iem_H_42.870_-96.350_1779061380000","source":"iem","severity":"low","severityValue":25,"timestamp":1779061380000,"latitude":42.87,"longitude":-96.35},{"id":"iem_H_43.200_-96.300_1779058260000","source":"iem","severity":"low","severityValue":25,"timestamp":1779058260000,"latitude":43.2,"longitude":-96.3},{"id":"iem_G_42.490_-96.060_1779065340000","source":"iem","severity":"low","severityValue":25,"timestamp":1779065340000,"latitude":42.49,"longitude":-96.06},{"id":"iem_T_42.310_-96.290_1779064260000","source":"iem","severity":"low","severityValue":25,"timestamp":1779064260000,"latitude":42.31,"longitude":-96.29},{"id":"iem_H_42.900_-96.310_1779061800000","source":"iem","severity":"low","severityValue":25,"timestamp":1779061800000,"latitude":42.9,"longitude":-96.31}] |
Safety Information
During flooding: never walk, swim, or drive through floodwaters. Six inches of moving water can knock you down, and one foot of water can sweep away a vehicle. Move to higher ground if waters rise. After flooding, avoid contact with floodwater which may contain sewage, chemicals, or debris. Follow local emergency service guidance.
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 39/100 (United States), based on data from noaa. Source: Calamity.live, a platform aggregating real-time data from 185 scientific monitoring sources.