This alert expired on 19 May 2026 at 22:30 UTC. It is kept here as a record.
It is the 5th strongest of the 103 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: Severe Thunderstorm Warning issued May 19 at 5:51PM EDT until May 19 at 6:30PM EDT by NWS Boston/Norton MA
An estimated 2,599,285 people live within 50 km of this point.
Nearby, since 16 March 2026
- August 8, 2026 · score 52 · 7.5 km
- August 8, 2026 · score 52 · 10.7 km
- May 19, 2026 · score 52 · 12.1 km
How we know
Confirmed by 3 independent sources, including NOAA.
Our own score for this event is 52 out of 100, at 91 % 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 | 91% |
| Coordinates | 42.2328, -71.6525 |
| Nearest City | Grafton (4 km) |
| Population Exposed | 2.6M within 50 km |
| Impact Tier | significant |
| Timestamp | 2026-05-19T21:51:00.000Z |
| Source | https://api.weather.gov/alerts/merged_Severe Thunderstorm Warning_noaa_urn:oid:2.49.0.1.840.0.1ea24d30ea03339987ea1ca8cf318312 |
Score Breakdown
Technical Details
| Event | Severe Thunderstorm Warning |
| Urgency | Immediate |
| Certainty | Observed |
| AreaDesc | Middlesex, MA; Norfolk, MA; Worcester, MA; Hampden, MA; Worcester, MA; Windham, CT; Middlesex, MA; Norfolk, MA; Worcester, MA; Providence, RI |
| Headline | Severe Thunderstorm Warning issued May 19 at 5:51PM EDT until May 19 at 6:30PM EDT by NWS Boston/Norton MA |
| Expires | 2026-05-19T18:30:00-04:00 |
| SenderName | NWS Boston/Norton MA |
| HasExactCoords | true |
| MergedCount | 3 |
| MergedIds | ["noaa_urn:oid:2.49.0.1.840.0.1ea24d30ea03339987ea1ca8cf318312cdca881f.001.1","noaa_urn:oid:2.49.0.1.840.0.998b96aa4517f0459e5715ec66931e2f6a878f45.001.1","noaa_urn:oid:2.49.0.1.840.0.383092258aac42ad05ce33a8ea509921ff4a325e.001.1"] |
| Google News RssFeed | weather |
| Google News SourceName | NBC Boston |
| MergedSources | [{"id":"gnews_weather_494224_159","source":"google_news","severity":"medium","severityValue":40,"timestamp":1779207960000,"latitude":42.36,"longitude":-71.06},{"id":"gnews_weather_494224_165","source":"google_news","severity":"medium","severityValue":40,"timestamp":1779209674000,"latitude":42.36,"longitude":-71.06}] |
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 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.
Want to know when something happens near Grafton?
Calamity.live data shows a weather event with CalamityScore 52/100, near Grafton (United States), based on data from noaa. Source: Calamity.live, a platform aggregating real-time data from 187 scientific monitoring sources.