This alert expired on 3 September 2026 at 21:45 UTC. It is kept here as a record.
It is the 4th strongest of the 5 detections recorded within 20 km of this point since 3 July 2026. Another comparable one was recorded here earlier the same day.
What the source measured
NOAA reported: Special Marine Warning issued September 3 at 3:43PM EDT until September 3 at 5:45PM EDT by NWS Detroit/Pontiac MI
An estimated 197,366 people live within 50 km of this point.
Nearby, since 3 July 2026
- July 3, 2026 · score 43 · 9.4 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.
Computed under scoring rules v4. Rows carrying other versions were judged by different rules and are not directly comparable.
Event Data
| Type | Severe Weather |
| Severity | Medium |
| Calamity Score (ours) | 37 / 100 |
| Our confidence | 81% |
| Coordinates | 42.3204, -82.3553 |
| Nearest City | Chatham (18 km) |
| Population Exposed | 197.4K within 50 km |
| Impact Tier | significant |
| Timestamp | 2026-09-03T19:43:00.000Z |
| Source | https://api.weather.gov/alerts/urn%3Aoid%3A2.49.0.1.840.0.a4fe7972a69ca6dba5978f8a7fbd453b774e1199.001.1 |
Score Breakdown
Technical Details
| Event | Special Marine Warning |
| Urgency | Immediate |
| Certainty | Likely |
| AreaDesc | Detroit River; Lake St. Clair Open Lake (U.S. Portion); Michigan Waters of Lake Erie from Detroit River to North Cape MI; Avon Point to Willowick OH; Willowick to Geneva-on-the Lake OH; Geneva-on-the-Lake to Conneaut OH; Conneaut OH to Ripley NY; Avon Point to Willowick OH beyond 5 nm off shoreline to US-Canadian border; Willowick to Geneva-on-the-Lake OH beyond 5NM off shoreline to US-Canadian border; Geneva-on-the-Lake to Conneaut OH beyond 5 nm off shoreline to US-Canadian border; Conneaut OH to Ripley NY beyond 5 nm off shoreline to US-Canadian border; St. Clair River; Harbor Beach to Port Sanilac MI; Port Sanilac to Port Huron MI; Lake Huron from Harbor Beach to Port Sanilac 5NM Off Shore to US/Canadian border; Lake Huron from Port Sanilac to Port Huron 5NM Off Shore to US/Canadian border |
| Headline | Special Marine Warning issued September 3 at 3:43PM EDT until September 3 at 5:45PM EDT by NWS Detroit/Pontiac MI |
| Expires | 2026-09-03T17:45:00-04:00 |
| SenderName | NWS Detroit/Pontiac MI |
| HasExactCoords | true |
| MergedCount | 3 |
| MergedIds | ["noaa_urn:oid:2.49.0.1.840.0.a4fe7972a69ca6dba5978f8a7fbd453b774e1199.001.1","noaa_urn:oid:2.49.0.1.840.0.de626632dd8c609b5ffede2498a11421d88a0a7f.001.1","noaa_urn:oid:2.49.0.1.840.0.adeef48251c067204c0e5d82025d4c5c47bb21f2.001.1"] |
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 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 near Chatham?
Calamity.live data shows a weather event with CalamityScore 37/100, near Chatham (Canada), based on data from noaa. Source: Calamity.live, a platform aggregating real-time data from 185 scientific monitoring sources.