This alert expired on 21 July 2026 at 08:15 UTC. It is kept here as a record.
It is the 4th strongest of the 102 detections recorded within 20 km of this point since 16 March 2026. Another comparable one was recorded here earlier the same day. 6 more were recorded here in the fortnight before it.
What the source measured
NOAA reported: Flash Flood Warning issued July 21 at 3:05AM CDT until July 21 at 3:15AM CDT by NWS Des Moines IA
An estimated 531,891 people live within 50 km of this point.
Nearby, since 16 March 2026
- June 11, 2026 · score 72 · 9.7 km
- June 11, 2026 · score 72 · 15.9 km
- June 11, 2026 · score 72 · 16.8 km
How we know
One source: NOAA. Not yet confirmed by a second, independent source.
Our own score for this event is 48 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) | 48 / 100 |
| Our confidence | 81% |
| Coordinates | 41.7200, -93.7617 |
| Nearest City | Johnston (8 km) |
| Population Exposed | 531.9K within 50 km |
| Impact Tier | significant |
| Timestamp | 2026-07-21T08:05:00.000Z |
| Source | https://api.weather.gov/alerts/urn:oid:2.49.0.1.840.0.c2935562805435067a489f1f211a2a1966f915b1.001.1 |
Score Breakdown
Technical Details
| Event | Flash Flood Warning |
| Urgency | Immediate |
| Certainty | Likely |
| AreaDesc | Dallas, IA; Polk, IA |
| Headline | Flash Flood Warning issued July 21 at 3:05AM CDT until July 21 at 3:15AM CDT by NWS Des Moines IA |
| Expires | 2026-07-21T03:15:00-05:00 |
| SenderName | NWS Des Moines IA |
| HasExactCoords | true |
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 Johnston?
Calamity.live data shows a weather event with CalamityScore 48/100, near Johnston (United States), based on data from noaa. Source: Calamity.live, a platform aggregating real-time data from 185 scientific monitoring sources.