This alert expired on 2 September 2026 at 04:00 UTC. It is kept here as a record.
It is the 208th strongest of the 241 detections recorded within 20 km of this point since 10 March 2026. The last comparable one was on 1 September 2026.
What the source measured
NOAA reported: Severe Thunderstorm Watch issued September 1 at 8:17PM CDT until September 1 at 11:00PM CDT by NWS Sioux Falls SD
An estimated 181,553 people live within 50 km of this point.
Nearby, since 10 March 2026
- September 2, 2026 · score 37 · 0.0 km
- September 1, 2026 · score 37 · 0.0 km
- August 13, 2026 · score 43 · 0.0 km
How we know
One source: NOAA. Not yet confirmed by a second, independent source.
Our own score for this event is 37 out of 100, at 81 % confidence.
The score is ours, computed from intensity, exposed population and local history — not the source’s.
Event Data
| Type | Severe weather |
| Severity | medium |
| Calamity Score (ours) | 37 / 100 |
| Our confidence | 81% |
| Coordinates | 42.0000, -93.2000 |
| Nearest City | Marshalltown (25 km) |
| Population Exposed | 181.6K within 50 km |
| Impact Tier | significant |
| Timestamp | 2026-09-02T01:17:00.000Z |
| Source | https://api.weather.gov/alerts/urn%3Aoid%3A2.49.0.1.840.0.df8bbe4db67b83f00877b46765064ef4a7242dfa.001.1 |
Score Breakdown
Technical Details
| Event | Severe Thunderstorm Watch |
| Urgency | Future |
| Certainty | Possible |
| AreaDesc | Cherokee, IA; Ida, IA; Woodbury, IA; Dakota, NE; Lyon, IA; Plymouth, IA; Sioux, IA; Pipestone, MN; Rock, MN; Dixon, NE; Aurora, SD; Bon Homme, SD; Charles Mix, SD; Clay, SD; Davison, SD; Douglas, SD; Gregory, SD; Hanson, SD; Hutchinson, SD; Lake, SD; Lincoln, SD; McCook, SD; Miner, SD; Minnehaha, SD; Moody, SD; Sanborn, SD; Turner, SD; Union, SD; Yankton, SD |
| Headline | Severe Thunderstorm Watch issued September 1 at 8:17PM CDT until September 1 at 11:00PM CDT by NWS Sioux Falls SD |
| Expires | 2026-09-01T23:00:00-05:00 |
| SenderName | NWS Sioux Falls SD |
| HasExactCoords | false |
| MergedCount | 2 |
| MergedIds | ["noaa_urn:oid:2.49.0.1.840.0.df8bbe4db67b83f00877b46765064ef4a7242dfa.001.1","noaa_urn:oid:2.49.0.1.840.0.df8bbe4db67b83f00877b46765064ef4a7242dfa.002.1"] |
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 10 February 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 near Marshalltown?
Calamity.live data shows a weather event with CalamityScore 37/100, near Marshalltown (United States), based on data from noaa. Source: Calamity.live, a platform aggregating real-time data from 185 scientific monitoring sources.