This alert expired on 21 July 2026 at 23:30 UTC. It is kept here as a record.
It is the 17th strongest of the 51 detections recorded within 20 km of this point since 12 June 2026. Another comparable one was recorded here earlier the same day. 7 more were recorded here in the fortnight before it.
What the source measured
NOAA reported: Flash Flood Warning issued July 21 at 4:21PM EDT until July 21 at 7:30PM EDT by NWS Upton NY
An estimated 18,653,056 people live within 50 km of this point.
Nearby, since 12 June 2026
- July 21, 2026 · score 46 · 7.3 km
- July 21, 2026 · score 46 · 8.9 km
- July 21, 2026 · score 46 · 10.2 km
How we know
One source: NOAA. Not yet confirmed by a second, independent source.
Our own score for this event is 46 out of 100, at 79 % 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) | 46 / 100 |
| Our confidence | 79% |
| Coordinates | 41.0992, -74.1158 |
| Nearest City | Mahwah (2 km) |
| Population Exposed | 18.7M within 50 km |
| Impact Tier | significant |
| Timestamp | 2026-07-21T20:21:00.000Z |
| Source | https://api.weather.gov/alerts/merged_Flash Flood Warning_noaa_urn:oid:2.49.0.1.840.0.644fa1ebdd545b023b48b7488dd4c072 |
Score Breakdown
Technical Details
| Event | Flash Flood Warning |
| Urgency | Immediate |
| Certainty | Likely |
| AreaDesc | Bronx, NY; Nassau, NY; Queens, NY; Suffolk, NY; Fairfield, CT; Westchester, NY; Hudson, NJ; Kings, NY; New York, NY; Queens, NY and 6 more areas |
| Headline | Flash Flood Warning issued July 21 at 4:21PM EDT until July 21 at 7:30PM EDT by NWS Upton NY |
| Expires | 2026-07-21T19:30:00-04:00 |
| SenderName | NWS Upton NY |
| HasExactCoords | true |
| MergedCount | 9 |
| MergedIds | ["noaa_urn:oid:2.49.0.1.840.0.644fa1ebdd545b023b48b7488dd4c072f9d14eeb.001.1","noaa_urn:oid:2.49.0.1.840.0.f69cd042ad8167a938448a9c4847aa09be832043.001.1","noaa_urn:oid:2.49.0.1.840.0.715d754a508814328cffb6ac641c0665e9bec213.001.1","noaa_urn:oid:2.49.0.1.840.0.707b2ad1f0c4bd0eeae7e8104d8182c181267021.001.1","noaa_urn:oid:2.49.0.1.840.0.5cc8b78d674185056fcd48e69f81151e2ee69280.001.1","noaa_urn:oid:2.49.0.1.840.0.09f87ad36671ae44019a3d186017d48fa40f0bd6.001.1","noaa_urn:oid:2.49.0.1.840.0.b0ef6fcf6aafa17ce5a0bb851b3f2f719f8b98c9.001.1","noaa_urn:oid:2.49.0.1.840.0.8f2a5d78aa0e63a8239c1a12541b92f3f9144c5d.001.1","noaa_urn:oid:2.49.0.1.840.0.8b322d9b64c3bd27e94ae01b96c72e8b5c97166c.001.1"] |
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 46/100, near Mahwah (United States), based on data from noaa. Source: Calamity.live, a platform aggregating real-time data from 188 scientific monitoring sources.