Severe weather near Greater Upper Marlboro
This alert expired on 18 July 2026 at 21:00 UTC. It is kept here as a record.
It is the 5th strongest of the 160 detections recorded within 20 km of this point since 17 March 2026. Another comparable one was recorded here earlier the same day. 16 more were recorded here in the fortnight before it.
What the source measured
NOAA reported: Special Marine Warning issued July 18 at 4:04PM EDT until July 18 at 5:00PM EDT by NWS Baltimore MD/Washington DC
An estimated 2,083,747 people live within 50 km of this point.
Nearby, since 17 March 2026
- June 12, 2026 · score 46 · 4.1 km
- March 20, 2026 · score 52 · 5.8 km
- March 17, 2026 · score 52 · 6.1 km
How we know
One source: NOAA. Not yet confirmed by a second, independent source.
Our own score for this event is 52 out of 100, at 80 % 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 | 80% |
| Coordinates | 38.6630, -76.5668 |
| Nearest City | Greater Upper Marlboro (24 km) |
| Population Exposed | 2.1M within 50 km |
| Impact Tier | significant |
| Timestamp | 2026-07-18T20:04:00.000Z |
| Source | https://api.weather.gov/alerts/merged_Special Marine Warning_noaa_urn:oid:2.49.0.1.840.0.c711e06273ba83e64fcc3e70c99acedb |
Score Breakdown
Technical Details
| Event | Special Marine Warning |
| Urgency | Immediate |
| Certainty | Likely |
| AreaDesc | Tidal Potomac from Indian Head to Cobb Island MD; Tidal Potomac from Cobb Island MD to Smith Point VA; Chesapeake Bay from North Beach to Drum Point MD; Chesapeake Bay from Drum Point MD to Smith Point VA; Patuxent River to Broomes Island MD; Tangier Sound and the inland waters surrounding Bloodsworth Island; Tidal Potomac from Cobb Island MD to Smith Point VA and 3 more areas |
| Headline | Special Marine Warning issued July 18 at 4:04PM EDT until July 18 at 5:00PM EDT by NWS Baltimore MD/Washington DC |
| Expires | 2026-07-18T17:00:00-04:00 |
| SenderName | NWS Baltimore MD/Washington DC |
| HasExactCoords | true |
| MergedCount | 6 |
| MergedIds | ["noaa_urn:oid:2.49.0.1.840.0.c711e06273ba83e64fcc3e70c99acedbfe9801cc.001.1","noaa_urn:oid:2.49.0.1.840.0.0714b2dbcff954fee1bd036ceae7e2d275973ca3.001.1","noaa_urn:oid:2.49.0.1.840.0.7c4506379f8ea48999a8ad663f487133c0d0d578.001.1","noaa_urn:oid:2.49.0.1.840.0.1331cf35f54e0f04514bd46e00fcf07a1d660307.001.1","noaa_urn:oid:2.49.0.1.840.0.5c804c7fdbb3b9e35b89487981bb48f15a3f1ec0.001.1","noaa_urn:oid:2.49.0.1.840.0.756c57abdab1148262931926a78e7f66c88ef89c.001.1"] |
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.
Calamity.live data shows a weather event with CalamityScore 52/100, near Greater Upper Marlboro (United States), based on data from noaa. Source: Calamity.live, a platform aggregating real-time data from 188 scientific monitoring sources.