Enhanced monsoonal moisture surged into Southern California, producing heavy thunderstorms across the San Bernardino County Mountains, the Riverside County Mountains and the San Diego County Mountains. A significant debris flow occurred on July 30 across northern portions of the El Dorado Burn Scar, with debris covering Highway 38.

Heavy Rain in RIVERSIDE, CALIFORNIA
From 30-JUL-21 14:45:00 to 30-JUL-21 14:45:00 (PST-8)
Location: IDYLLWILD
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Automated weather station at fire station reports 1.5 inches of rain in 60 minutes. 0.66 inches in 15 minutes.

Flood in SAN BERNARDINO, CALIFORNIA
From 30-JUL-21 14:15:00 to 30-JUL-21 14:15:00 (PST-8)
Location: YUCCA VLY GNT RCK AR
Flood cause: Heavy Rain
Property damage: 1.00K
Crop damage: 1.00K
Reported by: Trained Spotter

Spotter reported water flowing on Highway 247 Old Woman Springs Road. Radar estimates up to 1 inch of rain from thunderstorms.

Heavy Rain in RIVERSIDE, CALIFORNIA
From 30-JUL-21 13:30:00 to 30-JUL-21 15:00:00 (PST-8)
Location: ANZA
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Thomas Mountain hads gauge reports 2.56 inches of rainfall. Appears to be in about 60 to 90 minutes duration. This is located just south of Lake Hemet along Highway 74.

Lightning in SAN BERNARDINO, CALIFORNIA
From 31-JUL-21 11:30:00 to 31-JUL-21 12:30:00 (PST-8)
Location: BIG BEAR CITY
Property damage: 0.00K
Crop damage: 1.00K
Reported by: Park/Forest Service

A 200 year old Jeffery pine tree was struck by lightning. It burned later in the evening until extinguished. The large tree split in half while burning. The thunderstorm on radar appeared to be during several cloud to ground strikes near Big Bear airport around 1230 pm.

Dust Storm in SAN DIEGO COUNTY DESERTS, CALIFORNIA
From 30-JUL-21 20:00:00 to 30-JUL-21 20:30:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Twitter report with video of heavy blowing dust in Borrego Springs. Corresponding peak wind was 30 mph from the south-southeast at approximately 7 pm PDT. Minimum visibility unknown. Duration estimated.

Hail in SAN DIEGO, CALIFORNIA
From 31-JUL-21 13:35:00 to 31-JUL-21 13:35:00 (PST-8)
Location: (CZZ)CAMPO
Magnitude: 0.50 
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Public

A thunderstorm produced a layer of hail on the ground just north of Campo. Photos were shared. Some hail was around 1/2 inch diameter.

Flash Flood in SAN BERNARDINO, CALIFORNIA
From 30-JUL-21 12:35:00 to 30-JUL-21 18:30:00 (PST-8)
Location: SEVEN OAKS
Flood cause: Heavy Rain / Burn Area
Property damage: 10.00K
Crop damage: 10.00K
Reported by: Department of Highways

Significant debris flow occurred 1:30 to 2:00 pm on July 30 on Highway 38 along northern portions of the El Dorado burn scar. CalTrans reports road closure both directions on Highway 38 from Glass Road to Seven Oaks due to rock and mudslides on roadway. Restriction from Forest Falls to Lake Williams Drive. Radar has large thunderstorms over Highway 38 and Upper Santa Ana watershed estimated 2 to 2.5 inches of rain on radar in Frog Creek, Barton Creek and South Fork Santa Ana River.
Most significant flows occurred between PM 24.1 and 25.2, where boulders up to 1 m in diameter (potentially up to 2 m) moved. Net anchors initially held and restrained the initial surge of debris, but the volume eventually overtopped the nets and filled catchment basins. Debris overtopped a catchment basin at VAR EF0094 (west fork of the creek) and flowed onto the highway, resulting in a debris flow 150 feet wide and 5 feet deep.

Vehicles reported stuck and road is impassable at 3 locations. Highway 38 was closed for 7 hours due to several areas of debris flows. Large rocks, logs, mud and boulders being removed. Some damage reported to road. 4300 cubic yards or 400 truckloads were removed from Highway 38.