An influx of monsoonal moisture impacted portions of the southwestern U.S. from August 29th through 31st. This brought multiple thunderstorms from the deserts of Southern California all the way to the coast, where areas saw gusty winds, heavy rain, and frequent lightning. On August 30 and 31, severe thunderstorms impacted the Salton Sea and produce heavy rainfall. On August 31 a significant dust storm moved through the Coachella Valley and into the Borrego Deserts. On both days trees were reported downed in the lower Coachella Valley.

Thunderstorm Wind in SAN DIEGO, CALIFORNIA
From 29-AUG-21 13:30:00 to 29-AUG-21 14:30:00 (PST-8)
Location: RAMONA ARPT
Magnitude: 35.00 EG
Property damage: 0.00K
Crop damage: 1.00K
Reported by: Law Enforcement

Tree down at Mussey Grade and Mahogany Ranch roads in Ramona. The Ramona ASOS reported wind gusts near 40 MPH at the time from thunderstorm winds.

Thunderstorm Wind in SAN DIEGO, CALIFORNIA
From 29-AUG-21 13:30:00 to 29-AUG-21 14:30:00 (PST-8)
Location: RAMONA
Magnitude: 39.00 EG
Property damage: 0.00K
Crop damage: 3.00K
Reported by: Law Enforcement

Reported branches down on roadway and small trees near San Vincente Road and Wildcat Canyon Road in south Ramona. Wind gusts nearby 40 to 45 mph on mesonet.

Debris Flow in SAN DIEGO, CALIFORNIA
From 30-AUG-21 10:00:00 to 30-AUG-21 18:00:00 (PST-8)
Location: PINE VLY
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

CHP reports rock slides along the Sunrise Highway just north of Interstate 8.

Dust Storm in COACHELLA VALLEY, CALIFORNIA
From 30-AUG-21 18:30:00 to 30-AUG-21 19:30:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Thunderstorm outflow winds created blowing dust and sand across the southern Coachella Valley with wind gusts peaking at 50 MPH at the Thermal ASOS and visibility as low as three quarters of a mile. The Mesonet station UP633 in Mecca reported a wind gust of 34 MPH as well.

Heavy Rain in SAN BERNARDINO, CALIFORNIA
From 30-AUG-21 12:38:00 to 30-AUG-21 13:38:00 (PST-8)
Location: MORONGO LODGE
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Mesonet station KWYC1 Kenworthy RAWS reports 0.83 inches of rain in 1 hour from monsoon thunderstorms.

Debris Flow in SAN BERNARDINO, CALIFORNIA
From 30-AUG-21 13:00:00 to 30-AUG-21 18:00:00 (PST-8)
Location: MOONRIDGE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

Minor debris flow from thunderstorm rains occurred with rock and mud spilling onto State Highway 38. Radar estimates rain rate of one half inch an hour.

Astronomical Low Tide in APPLE AND LUCERNE VALLEYS, CALIFORNIA
From 30-AUG-21 14:00:00 to 30-AUG-21 22:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Fire Department/Rescue

Some areas in the mountains experienced small wildfires due to lightning strikes from monsoon thunderstorms. These were put out fairly quickly by fire officials.

Heavy Rain in SAN BERNARDINO, CALIFORNIA
From 30-AUG-21 09:30:00 to 30-AUG-21 12:00:00 (PST-8)
Location: MOONRIDGE
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Ski resort measures 0.75 inches of rain in one hour from monsoon thunderstorms.

Astronomical Low Tide in SAN DIEGO COUNTY MOUNTAINS, CALIFORNIA
From 30-AUG-21 11:25:00 to 30-AUG-21 12:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Pine Valley reports heavy rain in monsoon thunderstorms of 0.43 inches in a half hour.

Dust Storm in COACHELLA VALLEY, CALIFORNIA
From 31-AUG-21 14:00:00 to 31-AUG-21 18:00:00 (PST-8)
Property damage: 30.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Dust and low visibility was reported through out the Coachella Valley and Borrego Valley. Wind gusts 40 to 50 mph were observed from outflow of thunderstorms.

Flood in SAN DIEGO, CALIFORNIA
From 29-AUG-21 13:00:00 to 29-AUG-21 16:00:00 (PST-8)
Location: RAMONA ARPT
Flood cause: Heavy Rain
Property damage: 20.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Heavy rain from a strong thunderstorm moving east to west across the Ramona Valley caused minor flooding and downed small trees.

Lightning in SAN DIEGO, CALIFORNIA
From 29-AUG-21 15:00:00 to 29-AUG-21 18:00:00 (PST-8)
Location: CARDIFF BY THE SEA
Property damage: 20.00K
Crop damage: 0.00K
Reported by: Lifeguard

Lightning reached the beaches of San Diego County late in the afternoon August 29. This caused some beach closures and cancellation of outdoor activities. This photo captured by Del Mar lifeguards.

Lightning in SAN DIEGO, CALIFORNIA
From 30-AUG-21 12:00:00 to 30-AUG-21 17:00:00 (PST-8)
Location: WARNER SPGS
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Department of Highways

Lightning caused at least 3 wildfires reported by Caltrans (Quickmap). Fires were kept small due to rainfall and initial attack.

Dust Storm in SAN DIEGO COUNTY DESERTS, CALIFORNIA
From 31-AUG-21 16:00:00 to 31-AUG-21 19:00:00 (PST-8)
Property damage: 20.00K
Crop damage: 0.00K
Reported by: Department of Highways

A dust storm moved through the Borrego Valley on August 31. Dust was caught on area webcameras. Late afternoon thunderstorms caused the wind and dust. Very high levels of PM 2.5 and 10 were recorded by Anza Borrego Desert Research.

Thunderstorm Wind in RIVERSIDE, CALIFORNIA
From 31-AUG-21 16:00:00 to 31-AUG-21 17:00:00 (PST-8)
Location: MECCA
Magnitude: 30.00 EG
Property damage: 0.00K
Crop damage: 2.00K
Reported by: Mesonet

Large tree blocking the road near intersection of 66th Avenue/Box Canyon Road and Johnson Road in Mecca.

Thunderstorm Wind in RIVERSIDE, CALIFORNIA
From 31-AUG-21 16:00:00 to 31-AUG-21 17:00:00 (PST-8)
Location: MECCA
Magnitude: 30.00 EG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Strong thunderstorm winds resulted in roof damage at the Galilee Center, used as a shelter for people who had lost power the day before. The leaking roof prompted evacuation of the building.

Thunderstorm Wind in RIVERSIDE, CALIFORNIA
From 31-AUG-21 16:00:00 to 31-AUG-21 18:00:00 (PST-8)
Location: INDIAN WELLS
Magnitude: 39.00 EG
Property damage: 0.00K
Crop damage: 3.00K
Reported by: Department of Highways

A couple of trees were downed at La Quinta High School by high wind outflow from thunderstorms to the south. Southeast wind gusts 40 to 45 mph in the lower Coachella Valley were observed.

Thunderstorm Wind in RIVERSIDE, CALIFORNIA
From 31-AUG-21 16:00:00 to 31-AUG-21 18:00:00 (PST-8)
Location: MYOMA
Magnitude: 40.00 EG
Property damage: 0.00K
Crop damage: 1.00K
Reported by: Broadcast Media

Large tree blown down along Frank Sinatra Drive in Palm Desert. Another tree blown over onto a car.