This alert expired on 3 July 2026 at 23:51 UTC. It is kept here as a record.
It is the 2nd 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. One more was recorded here in the fortnight before it.
What the source measured
NOAA reported: Special Marine Warning issued July 3 at 7:41PM EDT until July 3 at 7:45PM EDT by NWS Detroit/Pontiac MI
An estimated 197,366 people live within 50 km of this point.
Nearby, since 3 July 2026
- September 3, 2026 · score 37 · 9.4 km
- July 3, 2026 · score 39 · 17.6 km
How we know
Confirmed by 2 independent sources, including NOAA.
Our own score for this event is 43 out of 100, at 84 % 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) | 43 / 100 |
| Our confidence | 84% |
| Coordinates | 42.2428, -82.4020 |
| Nearest City | Chatham (26 km) |
| Population Exposed | 197.4K within 50 km |
| Impact Tier | significant |
| Timestamp | 2026-07-03T23:41:00.000Z |
| Source | https://api.weather.gov/alerts/merged_Special Marine Warning_noaa_urn:oid:2.49.0.1.840.0.a24aea88e4eb9e1b81380d4b74c1b71e |
Score Breakdown
Technical Details
| Event | Special Marine Warning |
| Urgency | Immediate |
| Certainty | Likely |
| AreaDesc | St. Clair River; Lake St. Clair Open Lake (U.S. Portion); Vermilion to Avon Point OH; Avon Point to Willowick OH; Vermilion to Avon Point OH beyond 5 nm off shoreline to US-Canadian border; Avon Point to Willowick OH beyond 5 nm off shoreline to US-Canadian border; Reno Beach to The Islands OH; The Islands to Vermilion OH; Reno Beach to The Islands OH beyond 5NM off shoreline to US-Canadian border; The Islands to Vermilion OH beyond 5 nm off shoreline to US-Canadian border and 1 more areas |
| Headline | Special Marine Warning issued July 3 at 7:41PM EDT until July 3 at 7:45PM EDT by NWS Detroit/Pontiac MI |
| Expires | 2026-07-03T19:51:00-04:00 |
| SenderName | NWS Detroit/Pontiac MI |
| HasExactCoords | true |
| MergedCount | 4 |
| MergedIds | ["noaa_urn:oid:2.49.0.1.840.0.a24aea88e4eb9e1b81380d4b74c1b71ed043019b.001.1","noaa_urn:oid:2.49.0.1.840.0.2e4303a7dd612886a5996e6013694eded55a0b42.001.1","noaa_urn:oid:2.49.0.1.840.0.7ff4c7553c80113e6a301059bf407bc102985dfd.001.1","noaa_urn:oid:2.49.0.1.840.0.4561b12f376749ee1625bf6aa5117a55185212a4.001.1"] |
| Iem TypeSummary | G |
| Iem Magnitude | 63 |
| Iem Unit | mph |
| Iem City | Chesterfield |
| Iem County | Macomb |
| Iem State | MI |
| Iem Wfo | DTX |
| Iem Remark | Measured on a handheld anemometer |
| MergedSources | [{"id":"iem_G_42.660_-82.840_1783120380000","source":"iem","severity":"low","severityValue":25,"timestamp":1783120380000,"latitude":42.66,"longitude":-82.84}] |
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 43/100, near Chatham (Canada), based on data from noaa. Source: Calamity.live, a platform aggregating real-time data from 185 scientific monitoring sources.