This alert is in force until 3 September 2026, 04:15 UTC.
It is the 73rd strongest of the 89 detections recorded within 20 km of this point since 16 March 2026. The last comparable one was on 10 August 2026.
What the source measured
HEAT GOV reported: * WHAT...Heat index values up to 105 expected. * WHERE...Portions of southern Maryland, central, northern, and northwest Virginia, and panhandle West Virginia. * WHEN...From 11 AM to 7 PM EDT Thursday. * IMPACTS...Hot temperatures and high humidity may cause heat illnesses.
An estimated 632,079 people live within 50 km of this point.
Nearby, since 16 March 2026
- March 16, 2026 · score 67 · 9.2 km
- March 16, 2026 · score 72 · 11.8 km
- May 20, 2026 · score 43 · 16.0 km
How we know
One source: HEAT GOV. Not yet confirmed by a second, independent source.
Our own score for this event is 41 out of 100, at 68 % confidence.
The score is ours, computed from intensity, exposed population and local history — not the source’s.
Computed under scoring rules v4. Rows carrying other versions were judged by different rules and are not directly comparable.
Event Data
| Type | Severe Weather |
| Severity | Medium |
| Calamity Score (ours) | 41 / 100 |
| Our confidence | 68% |
| Coordinates | 38.9492, -77.8415 |
| Nearest City | South Riding (30 km) |
| Population Exposed | 632.1K within 50 km |
| Impact Tier | significant |
| Timestamp | 2026-09-03T15:00:00.000Z |
| Source | http://www.weather.gov |
Score Breakdown
Technical Details
| Event | Heat Advisory |
| Urgency | Expected |
| Certainty | Likely |
| Onset | 2026-09-03T11:00:00-04:00 |
| Expires | 2026-09-03T00:15:00-04:00 |
| AreaDesc | Charles; St. Marys; Calvert; Warren; Clarke; Stafford; King George; Northern Fauquier; Southern Fauquier; Northwest Prince William; Central and Southeast Prince William/Manassas/Manassas Park; Jefferson |
| SenderName | NWS Baltimore MD/Washington DC |
| ZonesUsedForCentroid | 5 |
| ZoneCount | 12 |
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 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 South Riding?
Calamity.live data shows a weather event with CalamityScore 41/100, near South Riding (United States), based on data from heat_gov. Source: Calamity.live, a platform aggregating real-time data from 185 scientific monitoring sources.