Right now
The most recent data we hold from NOAA arrived 23 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 31 July 2026 at 07:30 UTC. It is kept here as a record.
It is the 7th strongest of the 39 detections recorded within 20 km of this point since 15 March 2026. The last comparable one was on 9 July 2026.
What the source measured
NOAA reported: Flash Flood Warning issued July 30 at 11:34PM CDT until July 31 at 2:30AM CDT by NWS Sioux Falls SD
Urban PEI: 22,073 within a heuristic 50 km radius; not unique people.
Nearby, since 15 March 2026
- July 8, 2026 · score 34 · 18.3 km
- June 10, 2026 · score 58 · 24.1 km
How we know
One source: NOAA. Not yet confirmed by a second, independent source.
Our own score for this event is 34 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) | 34 / 100 |
| Legacy data-support index | 0.82/1 |
| Coordinates | 45.0086, -97.2730 |
| Nearest City | Watertown (17 km) |
| Urban exposure index (PEI) | 22.1K within 50 km |
| Impact Tier | significant |
| Timestamp | 2026-07-31T04:34:00.000Z |
| Source | https://api.weather.gov/alerts/merged_Flash Flood Warning_noaa_urn:oid:2.49.0.1.840.0.8fc0a1c28caf486c8c7bdc540931be82 |
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: 2026-07-31T04:34:00.000Z.
First archived: 2026-07-31T05:11:37.689Z. 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 | Kingsbury, SD; Big Stone, MN; Traverse, MN; Day, SD; Marshall, SD; Roberts, SD |
| Headline | Flash Flood Warning issued July 30 at 11:34PM CDT until July 31 at 2:30AM CDT by NWS Sioux Falls SD |
| Expires | 2026-07-31T02:30:00-05:00 |
| SenderName | NWS Sioux Falls SD |
| HasExactCoords | true |
| MergedCount | 2 |
| MergedIds | ["noaa_urn:oid:2.49.0.1.840.0.8fc0a1c28caf486c8c7bdc540931be82f2604798.001.1","noaa_urn:oid:2.49.0.1.840.0.1c5bbcf78a047e71ff4aa29c4d0c88dbb28510db.001.1"] |
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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