Right now
The most recent data we hold from NOAA arrived 5 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 18 May 2026 at 04:15 UTC. It is kept here as a record.
It is the 2nd strongest of the 61 detections recorded within 20 km of this point since 16 March 2026. Another comparable one was recorded here earlier the same day. 4 more were recorded here in the fortnight before it.
What the source measured
NOAA reported: Flash Flood Warning issued May 17 at 9:04PM CDT until May 17 at 11:15PM CDT by NWS Sioux Falls SD
Urban PEI: 82,821 within a heuristic 50 km radius; not unique people.
Nearby, since 16 March 2026
- September 12, 2026 · score 32 · 23.0 km
How we know
23 recorded sources include NOAA; independence is not established by this count.
Our own score for this event is 39 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) | 39 / 100 |
| Legacy data-support index | 0.90/1 |
| Coordinates | 42.8820, -96.1750 |
| Nearest City | Sioux City (46 km) |
| Urban exposure index (PEI) | 82.8K within 50 km |
| Impact Tier | significant |
| Timestamp | 2026-05-18T02:04:00.000Z |
| Source | https://api.weather.gov/alerts/urn:oid:2.49.0.1.840.0.d6fa0cbfb855b3ad17a63ebbd66e68dbd4da9915.001.1 |
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: 2026-05-18T02:04:00.000Z.
First archived: 2026-05-18T04:12:11.124Z. 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 | Flash Flood Warning |
| Urgency | Immediate |
| Certainty | Likely |
| AreaDesc | Plymouth, IA; Sioux, IA |
| Headline | Flash Flood Warning issued May 17 at 9:04PM 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_F_42.780_-96.180_1779066960000","source":"iem","severity":"low","severityValue":25,"timestamp":1779066960000,"latitude":42.78,"longitude":-96.18},{"id":"iem_T_42.820_-95.590_1779067740000","source":"iem","severity":"low","severityValue":25,"timestamp":1779067740000,"latitude":42.82,"longitude":-95.59},{"id":"iem_D_42.490_-96.370_1779063780000","source":"iem","severity":"low","severityValue":25,"timestamp":1779063780000,"latitude":42.49,"longitude":-96.37},{"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_42.890_-95.700_1779067740000","source":"iem","severity":"low","severityValue":25,"timestamp":1779067740000,"latitude":42.89,"longitude":-95.7},{"id":"iem_G_42.800_-95.630_1779067860000","source":"iem","severity":"low","severityValue":25,"timestamp":1779067860000,"latitude":42.8,"longitude":-95.63},{"id":"iem_H_43.140_-95.660_1779066540000","source":"iem","severity":"low","severityValue":25,"timestamp":1779066540000,"latitude":43.14,"longitude":-95.66},{"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_42.730_-95.550_1779067740000","source":"iem","severity":"low","severityValue":25,"timestamp":1779067740000,"latitude":42.73,"longitude":-95.55},{"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_H_43.460_-96.290_1779056040000","source":"iem","severity":"low","severityValue":25,"timestamp":1779056040000,"latitude":43.46,"longitude":-96.29},{"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.
Review the area, threshold and delivery channel in your account.
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