A significant surge of subtropical moisture arrived on the 29th ahead of a weather system coming up from Mexico. Combined with monsoonal moisture from the southeast, this resulted in scattered thunderstorms over the mountains, deserts, and portions of the Inland Empire each afternoon and evening through the 31st. Thunderstorms drifted into the Inland Empire from the adjacent mountains due to the easterly steering flow, as well as along the Elsinore Convergence Zone, in western Riverside County, on the 29th and 30th. The main area of flooding on the 29th occurred in the Riverside area, submerging vehicles and toppling large trees, due to rain-soaked ground and winds. The underpass along 14th Street west of Highway 91 experienced so much rain that it was still flooded the following morning. Though the Riverside Airport did not receive much in the way of rainfall; the gauge at UC Riverside received 1.2 inches of rain. The Inland Empire bore the brunt of the rainfall again on the 30th, adding to the existing flooding issues and creating new ones near Banning and Perris with flooded roadways and an RV park. The flooding in Banning was a debris flow from the Silver Fire burn scar. The only major flooding on the 31st was confined to the high desert along Highway 247 between Reche Road and Lynn Street.

Flash Flood in RIVERSIDE, CALIFORNIA
From 29-AUG-13 14:00:00 to 29-AUG-13 16:00:00 (PST-8)
Location: BOX SPGS
Flood cause: Heavy Rain
Property damage: 500.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Law enforcement reported that the 60 freeway was flooded, with 4 or 5 vehicles stuck in flood waters under the Market Street overpass. One motorist reported that the flood waters were moving his vehicle. Lanes 2, 3, and 4 of Highway 91 were flooded, with vehicles flooded out and sliding, including a school bus. Riverside City College cancelled classes due to flooding at the Landis Performing Arts Center and the campus quadrangle. Several other cars were flooded in parking lots near 14th Street, as well as basement flooding at a business there.

Flash Flood in RIVERSIDE, CALIFORNIA
From 30-AUG-13 14:30:00 to 30-AUG-13 17:00:00 (PST-8)
Location: BANNING
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Fire Department/Rescue

CHP reports flooded roadway and debris including rocks on Highway 243 south of Banning. Northbound traffic was closed. Further up the mountain off of 243, the Silent Valley RV Park had stranded residents due debris flows and flooding.

Flood in RIVERSIDE, CALIFORNIA
From 30-AUG-13 14:00:00 to 30-AUG-13 15:00:00 (PST-8)
Location: ALESSANDRO
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

CHP reported minor roadway flooding on Gavilan Road and Esperanza Drive, west of Perris.

Flash Flood in SAN BERNARDINO, CALIFORNIA
From 29-AUG-13 12:30:00 to 29-AUG-13 16:45:00 (PST-8)
Location: SILVERADO
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Fire Department/Rescue

Fire rescue officials reported that portions of Valley of the Falls Drive were closed due to water flowing over the road from Clarks Creek and Prospect Creek. Less than an hour later, fire officials reported that Prospect and Clarks Creeks were out of their banks. The intersection of Valley of the Falls Drive and Canyon Lane was also closed to all vehicles due to a mud slide.

Flash Flood in SAN BERNARDINO, CALIFORNIA
From 29-AUG-13 19:30:00 to 29-AUG-13 21:30:00 (PST-8)
Location: CUSHENBURY
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A spotter reported major flooding in dry washes and debris removal required on Highway 18 towards Big Bear at intersection of Camp Rock Road. The water was as deep as 2 feet in places. Another spotter reported water over another spot along Highway 18, estimated to be 50ft wide and more than 2 feet deep, with flow carrying boulders across the road. Up the mountain west of these locations, a spotter recorded a little over one inch of rain in 20 minutes and approximately 3 inches of water over some roadways.

Flash Flood in RIVERSIDE, CALIFORNIA
From 30-AUG-13 15:00:00 to 30-AUG-13 17:00:00 (PST-8)
Location: PERRIS
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

California Highway Patrol reported Orange Avenue from Murrieta Road to Evans Road, just northeast of Perris, was completely flooded and vehicles were not able to make it through. A nearby mesonet station recorded 0.69 inches of rain in 20 minutes.

Thunderstorm Wind in RIVERSIDE, CALIFORNIA
From 29-AUG-13 14:00:00 to 29-AUG-13 14:15:00 (PST-8)
Location: RIVERSIDE JCT
Magnitude: 61.00 EG
Property damage: 15.00K
Crop damage: 0.00K
Reported by: Public

An employee at UC Riverside estimated wind gusts up to 70 mph with very heavy rain and reduced visibility. Nearby, a large tree fell on the Rubidoux Boulevard off-ramp along Highway 60. Several other locations reported branches down, including a large tree that was uprooted and fell on a house along Chapman Street west of Magnolia Avenue.