A mesoscale convective system (organized thunderstorms) producing a dust storm (haboob) in the Imperial Valley, Salton Sea and Borrego deserts on the evening of August 10th. Visibility was reported as low as 1/2 mile to 1 mile observed. This was followed by hours of lightning and heavy rain in the deserts, mountains and even reaching the coast at the city of San Diego.  The system brought wind gusts 40 to 50 mph, heavy rainfall up to 2 inches in the San Diego mountains and desert slopes, and copious amounts of lightning with parts of the desert with localized flash flooding.  The southern coastal San Diego County received near one quarter of an inch.

Heavy Rain in SAN DIEGO, CALIFORNIA
From 10-AUG-21 21:00:00 to 11-AUG-21 06:00:00 (PST-8)
Location: BANNER
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

CNRFC's San Felipe station reports a total of 2.49 inches of rain.

Heavy Rain in SAN DIEGO, CALIFORNIA
From 10-AUG-21 21:00:00 to 11-AUG-21 06:00:00 (PST-8)
Location: RANCHITA
Property damage: 0.00K
Crop damage: 0.00K
Reported by: RAWS

The Ranchita RAWS measures 2.27 inches of rain, most which fell in two hours.

Heavy Rain in SAN DIEGO, CALIFORNIA
From 10-AUG-21 20:00:00 to 11-AUG-21 06:00:00 (PST-8)
Location: WHISPERING PINES
Property damage: 0.00K
Crop damage: 0.00K
Reported by: RAWS

Julian RAWS measures 0.70 inches of rain.

Heavy Rain in SAN DIEGO, CALIFORNIA
From 10-AUG-21 21:00:00 to 11-AUG-21 06:00:00 (PST-8)
Location: PINE HILLS
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Lake Cuyamaca measures 0.82 inches of rain.

Heavy Rain in SAN DIEGO, CALIFORNIA
From 10-AUG-21 21:00:00 to 11-AUG-21 06:00:00 (PST-8)
Location: OCOTILLO WELLS
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Ocotillo Wells reports 0.84 inches of rain.

Heavy Rain in SAN DIEGO, CALIFORNIA
From 10-AUG-21 21:00:00 to 11-AUG-21 06:00:00 (PST-8)
Location: JULIAN
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Volcan Mountain measures 1.26 inches of rain.

Heavy Rain in SAN DIEGO, CALIFORNIA
From 10-AUG-21 22:00:00 to 11-AUG-21 06:00:00 (PST-8)
Location: MT LAGUNA AFS
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Mason Valley station reports 1.84 inches of rain.

Heavy Rain in SAN DIEGO, CALIFORNIA
From 10-AUG-21 21:00:00 to 11-AUG-21 06:00:00 (PST-8)
Location: BORREGO SPGS
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

CNRFC site Coyote Canyon Creek measures 1.66 inches of rain.

Flash Flood in SAN DIEGO, CALIFORNIA
From 10-AUG-21 22:00:00 to 11-AUG-21 20:00:00 (PST-8)
Location: DESERT LODGE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Reports of water and mud covered Borrego Valley Airport after the storm's heavy rainfall. Pilots were not able to land on the runway. The airport also reported blowing dust with two miles of visibility and a wind gust to 40 mph.

Flash Flood in SAN DIEGO, CALIFORNIA
From 10-AUG-21 21:00:00 to 11-AUG-21 00:00:00 (PST-8)
Location: DESERT LODGE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

CHP reports flash flooding at Borrego Salton Seaway road at Fonts wash, where a car was stuck in the low water crossing.

Heavy Rain in SAN DIEGO, CALIFORNIA
From 10-AUG-21 11:15:00 to 10-AUG-21 12:15:00 (PST-8)
Location: PALOMAR MTN
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

A thunderstorm produced heavy rainfall at Palomar Mountain RAWS. 1.09 inches of rain fell from 12:15 pm-1:15 pm.

Thunderstorm Wind in SAN DIEGO, CALIFORNIA
From 11-AUG-21 00:00:00 to 11-AUG-21 00:25:00 (PST-8)
Location: MESA GRANDE
Magnitude: 50.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Big Black Mountain measures thunderstorm wind gust of 57 MPH.

Thunderstorm Wind in RIVERSIDE, CALIFORNIA
From 10-AUG-21 22:00:00 to 11-AUG-21 00:00:00 (PST-8)
Location: MYOMA
Magnitude: 26.00 EG
Property damage: 0.00K
Crop damage: 10.00K
Reported by: Broadcast Media

Large tree downed on Tamarisk Row by strong winds. Reported by KESQ TV.

Flash Flood in SAN DIEGO, CALIFORNIA
From 10-AUG-21 22:00:00 to 11-AUG-21 07:00:00 (PST-8)
Location: BORREGO SPGS
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Flash flooding reported by Desert Research Institute officials morning after heavy rains went through the area. Monsoon storms led to flash flooding of Coyote Canyon and adjacent citrus tree fields.

Dust Storm in SAN DIEGO COUNTY DESERTS, CALIFORNIA
From 10-AUG-21 17:00:00 to 11-AUG-21 01:00:00 (PST-8)
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Department of Highways

A dust storm (haboob) moved across the San Diego Deserts from east to west and originated in the Imperial Valley and southeast California ahead of organized thunderstorms. Visibility went to 1/2 mile in the deserts before heavy rain occurred.

Lightning in SAN BERNARDINO, CALIFORNIA
From 10-AUG-21 12:00:00 to 10-AUG-21 18:00:00 (PST-8)
Location: MOONRIDGE
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Fire Department/Rescue

Lightning caused 6 wildfires starts despite heavy rain. The wildfires were contained and kept to small acreage.