This alert expired on 21 June 2026 at 00:15 UTC. It is kept here as a record.
No stronger detection stands among the 13 recorded within 20 km of this point since 23 May 2026 — 8 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: Flash Flood Warning issued June 20 at 6:09PM CDT until June 20 at 7:15PM CDT by NWS Houston/Galveston TX
An estimated 3,415,455 people live within 50 km of this point.
Nearby, since 23 May 2026
- May 23, 2026 · score 52 · 12.6 km
- May 23, 2026 · score 52 · 13.8 km
- August 28, 2026 · score 52 · 14.3 km
How we know
Confirmed by 2 independent sources, including NOAA.
Our own score for this event is 52 out of 100, at 84 % confidence.
The score is ours, computed from intensity, exposed population and local history — not the source’s.
Event Data
| Type | Severe weather |
| Severity | medium |
| Calamity Score (ours) | 52 / 100 |
| Our confidence | 84% |
| Coordinates | 29.3872, -95.4072 |
| Nearest City | Alvin (17 km) |
| Population Exposed | 3.4M within 50 km |
| Impact Tier | significant |
| Timestamp | 2026-06-20T23:09:00.000Z |
Score Breakdown
Technical Details
| Event | Flash Flood Warning |
| Urgency | Immediate |
| Certainty | Likely |
| AreaDesc | Brazoria, TX; Galveston, TX; Harris, TX; Brazoria, TX; Fort Bend, TX |
| Headline | Flash Flood Warning issued June 20 at 6:09PM CDT until June 20 at 7:15PM CDT by NWS Houston/Galveston TX |
| Expires | 2026-06-20T19:15:00-05:00 |
| SenderName | NWS Houston/Galveston TX |
| HasExactCoords | true |
| MergedCount | 2 |
| MergedIds | ["noaa_urn:oid:2.49.0.1.840.0.17e27b14892790f68b7f5e777e7c8811602bdb74.001.1","noaa_urn:oid:2.49.0.1.840.0.df4d4706dfeea1992c83e333c26520494b77ac75.001.1"] |
| Iem TypeSummary | M |
| Iem Magnitude | 49 |
| Iem Unit | MPH |
| Iem City | 6 ENE San Leon |
| Iem County | GMZ335 |
| Iem State | TX |
| Iem Wfo | HGX |
| Iem Remark | 43 knot wind gust at Weatherflow station XGAL. |
| MergedSources | [{"id":"iem_M_29.520_-94.850_1781992500000","source":"iem","severity":"low","severityValue":25,"timestamp":1781992500000,"latitude":29.52,"longitude":-94.85}] |
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 10 February 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.
Calamity.live data shows a weather event with CalamityScore 52/100, near Alvin (United States), based on data from noaa. Source: Calamity.live, a platform aggregating real-time data from 191 scientific monitoring sources.