Heavy Rain, Montgomery
- When
- September 7, 7:00 PM EST to 9:00 PM EST
- Where
- Montgomery County, Gaithersburg
- Reported by
- NEWSPAPER
- Coordinates
- 39.136, -77.204 (the zone’s center; the record gives no point)
Streets flooded
Damaging Winds and Heavy Rain in Maryland, September 7, 1999
Just a few days after Hurricane Dennis dropped heavy rain over North Central Maryland, another area of thunderstorms moved across the area producing winds in excess of 55 MPH, frequent lightning, and very heavy downpours. The storms affected the area between 8:00 PM and 10:00 PM EDT.
Where it happened
Every event with a place to put it; 1 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
- Tornadoes
- Tropical storms and surge
- Floods
- Wind
- Hail
- Winter weather
- Heat and drought
- Cold
- Fire, smoke and dust
- Marine and coastal
- Other
The toll
- Deaths
- 0
- Injuries
- 0
- Property damage
- $6,000
- Crop damage
- None recorded
- Events
- 3
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
What happened
The episode as NWS LWX wrote it up.
Just a few days after Hurricane Dennis dropped heavy rain over North Central Maryland, another area of thunderstorms moved across the area producing winds in excess of 55 MPH, frequent lightning, and very heavy downpours. The storms affected the area between 8:00 PM and 10:00 PM EDT. High winds downed trees in Frederick and Montgomery Counties. Winds gusted to 50 MPH in Mt. Airy and 0.91 inches of rain fell in 20 minutes. Heavy downpours produced minor street flooding in Gaithersburg around 9:00 PM EDT. Power outages were also reported.
The radar
The national radar mosaic for the moment the first event began.
Event by event
2 thunderstorm wind, 1 heavy rain. Local standard time, as filed.
Thunderstorm Wind, Frederick
- When
- September 7, 7:20 PM EST to 7:40 PM EST
- Where
- Frederick County, South Portion
- Property damage
- $3,000
- Reported by
- NEWSPAPER
- Coordinates
- 39.350, -77.420
Trees downed across roads
Thunderstorm Wind, Montgomery
- When
- September 7, 7:45 PM EST
- Where
- Montgomery County, Gaithersburg
- Property damage
- $3,000
- Reported by
- LAW ENFORCEMENT
- Coordinates
- 39.130, -77.200
Trees downed onto power lines
What these are
- Heavy Rain
- Rainfall totals unusual for the place and season that did not produce a flood.
- Thunderstorm Wind
- Winds from a thunderstorm of 50 knots (58 mph) or more, or lower winds that caused damage or casualties. Measured gusts are marked MG, estimated EG.
After NWS Directive 10-1605, the rules offices file Storm Data by.
The same day elsewhere
- Flash Flood in Pennsylvania, September 7, 1999
- Tornado and Hail in Iowa, September 7, 1999
- Flash Flood in Pennsylvania, September 7, 1999
- Flash Flooding and Hail in Oklahoma, September 7, 1999
- Hail and Damaging Winds in Oklahoma, September 7 to 8, 1999
- Hail and Damaging Wind in Georgia, September 7, 1999
- Flood in Florida, September 7, 1999
- Flash Flooding and Hail in Virginia, September 7, 1999
- Damaging Wind in Louisiana, September 7, 1999
- Flash Flood in Pennsylvania, September 7, 1999
- Damaging Wind in West Virginia, September 7, 1999
- Hail in Minnesota, September 7, 1999
More
Every storm in Maryland in 1999Every state in 1999This day in weather historyWarnings in Maryland, September 1999
Sources
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 5718283, 5718282, 5718284.