This alert expired on 21 May 2026 at 03:45 UTC. It is kept here as a record.
It is the 9th strongest of the 37 detections recorded within 20 km of this point since 15 March 2026. The last comparable one was on 21 May 2026. 19 more were recorded here in the fortnight before it.
What the source measured
NOAA reported: Flood Warning issued May 20 at 2:48PM EDT until May 20 at 11:45PM EDT by NWS Indianapolis IN
An estimated 429,137 people live within 50 km of this point.
Nearby, since 15 March 2026
- May 21, 2026 · score 48 · 5.4 km
- June 1, 2026 · score 43 · 13.0 km
- July 11, 2026 · score 48 · 14.2 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, at 81 % 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 | 81% |
| Coordinates | 39.0707, -90.7437 |
| Nearest City | O'Fallon (29 km) |
| Population Exposed | 429.1K within 50 km |
| Impact Tier | significant |
| Timestamp | 2026-05-22T04:17:00.000Z |
| Source | https://api.weather.gov/alerts/merged_Flood Warning_noaa_urn:oid:2.49.0.1.840.0.00ce4b41f16046c97bd76fdfd53e412d |
Score Breakdown
Technical Details
| Event | Flood Warning |
| Urgency | Expected |
| Certainty | Likely |
| AreaDesc | Decatur, IN; Rush, IN; Daviess, IN; Greene, IN; Knox, IN; Martin, IN; Clinton, IL and 39 more areas |
| Headline | Flood Warning issued May 20 at 2:48PM EDT until May 20 at 11:45PM EDT by NWS Indianapolis IN |
| Expires | 2026-05-20T23:45:00-04:00 |
| SenderName | NWS Indianapolis IN |
| HasExactCoords | true |
| MergedCount | 46 |
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Safety Information
During flooding: never walk, swim, or drive through floodwaters. Six inches of moving water can knock you down, and one foot of water can sweep away a vehicle. Move to higher ground if waters rise. After flooding, avoid contact with floodwater which may contain sewage, chemicals, or debris. Follow local emergency service guidance.
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 O'Fallon?
Calamity.live data shows a weather event with CalamityScore 43/100, near O'Fallon (United States), based on data from noaa. Source: Calamity.live, a platform aggregating real-time data from 185 scientific monitoring sources.