Right now
The most recent data we hold from NOAA arrived 4 minutes ago, and this point is not in it. We record detections, not passes: an absence is not proof that nothing is there.
11 other detections within 20 km in the last 24 hours, the nearest <1 km from here.
This alert expired on 17 September 2026 at 21:30 UTC. It is kept here as a record.
No stronger detection stands among the 75 recorded within 20 km of this point since 15 March 2026 — 7 others scored the same. The last comparable one was on 16 September 2026. 3 more were recorded here in the fortnight before it.
What the source measured
NOAA reported: Severe Thunderstorm Warning issued September 17 at 3:38PM CDT until September 17 at 4:30PM CDT by NWS St Louis MO
Urban PEI: 767,216 within a heuristic 50 km radius; not unique people.
Nearby, since 15 March 2026
- September 17, 2026 · score 54 · 0.0 km
- September 18, 2026 · score 54 · 5.0 km
- June 8, 2026 · score 52 · 12.2 km
How we know
3 recorded sources include NOAA; independence is not established by this count.
Our own score for this event is 54 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 v5. Rows carrying other versions were judged by different rules and are not directly comparable.
Event Data
| Type | Severe Weather |
| Severity | High |
| Calamity Score (ours) | 54 / 100 |
| Legacy data-support index | 0.92/1 |
| Coordinates | 38.8810, -90.7155 |
| Nearest City | O'Fallon (8 km) |
| Urban exposure index (PEI) | 767.2K within 50 km |
| Impact Tier | severe |
| Timestamp | 2026-09-17T20:38:00.000Z |
| Source | https://api.weather.gov/alerts/urn%3Aoid%3A2.49.0.1.840.0.bbab5ce0d014a00b9348050620d291fe3908d3cb.001.1 |
Physical priority index · v5. 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: 2026-09-17T20:38:00.000Z.
First archived: 2026-09-17T20:43:58.866Z. Material modification: 2026-09-17T20:49:35.001Z.
Retained revisions are prospective; earlier versions may be unavailable. No revision entry does not prove that a record never changed.
2026-09-17T20:54:56.976Z · data_change
Index 54 → 54; severity high → high; version 5 → 5.
2026-09-17T20:49:35.001Z · data_change
Index 41 → 54; severity medium → high; version 5 → 5.
Score Breakdown
Technical Details
| Event | Severe Thunderstorm Warning |
| Urgency | Immediate |
| Certainty | Observed |
| AreaDesc | St. Charles, MO |
| Headline | Severe Thunderstorm Warning issued September 17 at 3:38PM CDT until September 17 at 4:30PM CDT by NWS St Louis MO |
| Expires | 2026-09-17T16:30:00-05:00 |
| SenderName | NWS St Louis MO |
| HasExactCoords | true |
| Spc ReportType | hail |
| Spc Speed | 100 |
| Spc Location | 1 SW Saint Paul |
| Spc County | St. Charles |
| Spc State | MO |
| Spc Comments | (LSX) |
| Iem TypeSummary | H |
| Iem Magnitude | 1 |
| Iem Unit | Inch |
| Iem City | 1 SW Saint Paul |
| Iem County | St. Charles |
| Iem State | MO |
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.
Review the area, threshold and delivery channel in your account.
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