Right now
The most recent data we hold from NOAA arrived 33 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 21:45 UTC. It is kept here as a record.
No stronger detection stands among the 18 recorded within 20 km of this point since 4 April 2026 — 2 others scored the same. 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: Severe Thunderstorm Warning issued May 18 at 5:31PM EDT until May 18 at 5:45PM EDT by NWS Detroit/Pontiac MI
Urban PEI: 101,455 within a heuristic 50 km radius; not unique people.
Nearby, since 4 April 2026
- May 18, 2026 · score 43 · 0.6 km
- July 21, 2026 · score 22 · 16.9 km
How we know
One source: NOAA. Not yet confirmed by a second, independent source.
Our own score for this event is 43 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) | 43 / 100 |
| Legacy data-support index | 0.79/1 |
| Coordinates | 43.3291, -82.6943 |
| Nearest City | Sarnia (46 km) |
| Urban exposure index (PEI) | 101.5K within 50 km |
| Impact Tier | significant |
| Timestamp | 2026-05-18T21:31:00.000Z |
| Source | https://api.weather.gov/alerts/merged_Severe Thunderstorm Warning_noaa_urn:oid:2.49.0.1.840.0.8546f0614e4f255ecf847f9ebeed0ff3 |
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: 2026-05-18T21:31:00.000Z.
First archived: 2026-05-18T21:39:24.297Z. 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 | Severe Thunderstorm Warning |
| Urgency | Immediate |
| Certainty | Observed |
| AreaDesc | Huron, MI; Macomb, MI; St. Clair, MI; Sanilac, MI |
| Headline | Severe Thunderstorm Warning issued May 18 at 5:31PM EDT until May 18 at 5:45PM EDT by NWS Detroit/Pontiac MI |
| Expires | 2026-05-18T17:45:00-04:00 |
| SenderName | NWS Detroit/Pontiac MI |
| HasExactCoords | true |
| MergedCount | 3 |
| MergedIds | ["noaa_urn:oid:2.49.0.1.840.0.8546f0614e4f255ecf847f9ebeed0ff3a678accb.001.1","noaa_urn:oid:2.49.0.1.840.0.6703aeb65ae6515d0f319611dd2b01dc2bb68159.001.1","noaa_urn:oid:2.49.0.1.840.0.2b61f34f418d775e6bf2cfbf433f71b7656a61cb.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.
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