A deep southerly fetch of rich moisture up from the Gulf of California led to scattered to widespread heavy rainfall in Imperial and eastern Riverside counties during the afternoon of the 1st. Moisture values were well above normal for the time of year with precipitable water values analyzed around 2.0-2.2 inches. A Flash Flood Watch was issued for much of the region. Favorable dynamic and orographic forcing helped lead to strong updrafts and training of storms over certain terrain areas. Radar estimated rain rates were up to around 2-3 inches per hour with locally higher rates over shorter periods. There was a RAWS station in eastern Imperial County that measured right around 3 inches in 1 hour. These high rain rates led to areas of high rainfall accumulation, with many areas seeing at least 1 inch of rain and isolated areas up to 3.5-4.5 inches, radar estimated. This resulted in numerous reports of considerable flash flooding around the region. The hardest hit was the town of Niland and immediate surrounding area. A few inches of rain fell east of Niland leading to a canal being overcome with water and silt. This exacerbated the flooding and several inches of water flowed through the town and surrounding areas. The major impacts led to an emergency proclamation by the County of Imperial. In addition to the road closures, there were several swift water rescues across Imperial and Riverside Counties, both by land and air. One of the air rescues was completed by the San Diego US Coast Guard. On top of all the flooding, the heavy mass loading and strong updrafts resulted in strong to severe downburst winds, which caused a couple semi truck rollovers, downed many power poles, and generated dense  blowing dust.

Flash Flood in IMPERIAL, CALIFORNIA
From 01-SEP-23 13:07:00 to 01-SEP-23 18:30:00 (PST-8)
Location: CACTUS
Flood cause: Heavy Rain
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Department of Highways

Ogilby Road, a flood-prone road, was closed between I-8 and Hwy-78 due to flooding. A later report said there were chunks of road washed out. A photo shared by Caltrans on September 2nd showed water still flowing over the road and a construction vehicle cleaning up large amounts of debris on the roadway.  No injuries or specific magnitude of damages were reported.

Flash Flood in IMPERIAL, CALIFORNIA
From 01-SEP-23 13:57:00 to 01-SEP-23 17:00:00 (PST-8)
Location: DIXIELAND
Flood cause: Heavy Rain
Property damage: 21.00K
Crop damage: 0.00K
Reported by: Department of Highways

A sedan was swept off Dunaway Rd, just south of Evan Hughes Hwy, due to a flooded wash. A photo shows a man in more than waist-deep water trying to push the floating sedan. First responders had a difficult time getting to the scene due to flooding. Dunaway Rd was also closed between Evan Hughes Hwy and I-8. No injuries were reported. Damage cost based on car value.

Flash Flood in IMPERIAL, CALIFORNIA
From 01-SEP-23 13:36:00 to 01-SEP-23 17:30:00 (PST-8)
Location: PALO VERDE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

Report for California Highway Patrol of an unknown number of vehicles stuck on Hwy-78 due to flooding. No injuries or damages reported.

Flash Flood in IMPERIAL, CALIFORNIA
From 01-SEP-23 13:38:00 to 01-SEP-23 17:30:00 (PST-8)
Location: PICACHO
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

California Highway Patrol incident reports indicated there were vehicles stuck in and/or in between flooded washes on Black Mountain Rd. No injuries or damages were reported.

Flash Flood in IMPERIAL, CALIFORNIA
From 01-SEP-23 12:51:00 to 01-SEP-23 13:30:00 (PST-8)
Location: GLAMIS
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

An incident report from California Highway Patrol said that multiple vehicles were stopped due to flooding on Highway 78. No injuries or damages were reported.

Thunderstorm Wind in IMPERIAL, CALIFORNIA
From 01-SEP-23 12:51:00 to 01-SEP-23 12:51:00 (PST-8)
Location: (IPL)IMPERIAL CO ARP
Magnitude: 52.00 EG
Property damage: 7.00K
Crop damage: 0.00K
Reported by: Department of Highways

Semi truck flipped and on its side due to strong winds. Winds estimated at 60 mph. No injuries were reported.

Flash Flood in RIVERSIDE, CALIFORNIA
From 01-SEP-23 13:20:00 to 01-SEP-23 18:30:00 (PST-8)
Location: MESAVILLE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

An incident report from California Highway Patrol said there was flooding along Hwy-95, prompting a call for a potential closure of the highway. No injuries or damages were reported.

Flash Flood in IMPERIAL, CALIFORNIA
From 01-SEP-23 14:20:00 to 01-SEP-23 18:30:00 (PST-8)
Location: GLAMIS
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

Hwy-78 was closed between the Imperial and Riverside County line and Ogilby Rd due to many flooded washes. Many vehicles were stopped along the highway due to impassable flooded washes. Hwy-78 did not fully reopen until the morning of September 3rd due to debris cleanup. No injuries or damages were reported.

Flash Flood in RIVERSIDE, CALIFORNIA
From 01-SEP-23 15:33:00 to 01-SEP-23 19:00:00 (PST-8)
Location: MORTMAR
Flood cause: Heavy Rain
Property damage: 20.00K
Crop damage: 0.00K
Reported by: Department of Highways

Incident report from California Highway Patrol of a compromised bridge along Hwy-111 near Mecca Ave being washed out due to flooding. Also a report of a trapped party along Club View Dr. In this same area there was also a report of 2-3 vehicles being taken out by flash flooding.  Additional flooding led to Hwy-111 being closed down to the Imperial county line. No injuries or damages were reported.

Dust Storm in IMPERIAL COUNTY SOUTHEAST, CALIFORNIA
From 01-SEP-23 13:00:00 to 01-SEP-23 15:30:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Newspaper

Photos showed visibility dropped below 1/4 mile in blowing dust and sand along I-8 with winds gusting to 40 to 50 mph behind a strong outflow boundary. The strong gusts and reduced visibilities lasted for over 1 hour. No accidents were reported.

Flash Flood in RIVERSIDE, CALIFORNIA
From 01-SEP-23 14:11:00 to 01-SEP-23 17:30:00 (PST-8)
Location: DESERT CENTER ARPT
Flood cause: Heavy Rain
Property damage: 20.00K
Crop damage: 0.00K
Reported by: Department of Highways

A California Highway Patrol incident report said there were 5 vehicles stuck in flooded washes on Hwy-177. Some of the occupants may have had to be rescued and there was a call to close the highway. No injuries were reported and specifics on vehicle damage was not shared.

Thunderstorm Wind in IMPERIAL, CALIFORNIA
From 01-SEP-23 13:12:00 to 01-SEP-23 13:12:00 (PST-8)
Location: IMPERIAL
Magnitude: 52.00 EG
Property damage: 15.00K
Crop damage: 0.00K
Reported by: Department of Highways

Several power poles were reported knocked over and nearly in the road along Highway 111 between Aten and Worthington Roads. Winds estimated at 60 mph. No injuries were reported.

Thunderstorm Wind in IMPERIAL, CALIFORNIA
From 01-SEP-23 13:19:00 to 01-SEP-23 13:19:00 (PST-8)
Location: SALTON CITY
Magnitude: 52.00 EG
Property damage: 7.00K
Crop damage: 0.00K
Reported by: Department of Highways

A semi-truck rolled over on Highway 86 due to strong winds and blocked both lanes of traffic. Winds were estimated at 60 mph. No injuries were reported, but medical was called to the scene.

Flash Flood in IMPERIAL, CALIFORNIA
From 01-SEP-23 14:30:00 to 01-SEP-23 19:00:00 (PST-8)
Location: PALO VERDE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: County Official

Walters Camp Rd was closed due to flooding between Hwy-78 and the Colorado River. Sentinel2 before and after satellite imagery showed evidence of considerable flow within Milpitas Wash, which Walters Camp Rd parallels and cuts across. No damages or injuries were reported. Timing estimated from radar.

Flash Flood in IMPERIAL, CALIFORNIA
From 01-SEP-23 15:30:00 to 01-SEP-23 19:00:00 (PST-8)
Location: NILAND
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: County Official

Coachella Canal Rd, a dirt road, was closed between approximately Siphon 17 and Siphon 7 of the Coachella Canal due to flooding. No damages or injuries were reported. Timing estimated from radar.

Thunderstorm Wind in IMPERIAL, CALIFORNIA
From 01-SEP-23 12:51:00 to 01-SEP-23 12:51:00 (PST-8)
Location: (IPL)IMPERIAL CO ARP
Magnitude: 52.00 EG
Property damage: 15.00K
Crop damage: 0.00K
Reported by: Newspaper

Multiple large trees were toppled on the campus of Imperial Valley College. The college also lost power, due to nearby downed powerlines, and sustained damage to their fiber optic network. This led to the closure of the school. Winds were estimated around 60 mph. No injuries were reported.

Flash Flood in IMPERIAL, CALIFORNIA
From 01-SEP-23 14:00:00 to 01-SEP-23 18:30:00 (PST-8)
Location: OCOTILLO
Flood cause: Heavy Rain
Property damage: 20.00K
Crop damage: 0.00K
Reported by: Department of Highways

A couple rounds of heavy rain resulted in considerable flooding and the closure of Hwy-98 between S2 and Brockman Rd. Along Hwy-98, 2 vehicles became stuck in a flooded wash, with one occupant having to climb out onto their roof. No injuries were reported and the extent of damage to the vehicles is unknown. Timing was adjusted based on radar.

Flash Flood in IMPERIAL, CALIFORNIA
From 01-SEP-23 16:10:00 to 01-SEP-23 19:30:00 (PST-8)
Location: IMPERIAL
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

Forrester Rd, near Larsen Rd, was closed due to flooding. No damages or injuries were reported. Timing estimated from radar.

Flash Flood in IMPERIAL, CALIFORNIA
From 01-SEP-23 14:20:00 to 01-SEP-23 16:20:00 (PST-8)
Location: (IPL)IMPERIAL CO ARP
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

Old Hwy 111 was closed due to flooding between Aten Rd and Evan Hughes Rd. No damages or injuries were reported. Timing estimated from radar.

Flash Flood in IMPERIAL, CALIFORNIA
From 01-SEP-23 14:05:00 to 01-SEP-23 17:00:00 (PST-8)
Location: DIXIELAND
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: County Official

Wheeler Rd was closed due to flooding between Imler Rd and Huff Rd. No damages or injuries were reported. Timing estimated from radar.

Flash Flood in IMPERIAL, CALIFORNIA
From 01-SEP-23 14:50:00 to 01-SEP-23 19:00:00 (PST-8)
Location: ESTELLE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

Blair Rd at Schrimpf Rd was closed due to flooding. Schrimpf Rd and Weist Rd were also closed around their intersection. No injuries or damages were reported. Time based on radar.

Flash Flood in IMPERIAL, CALIFORNIA
From 01-SEP-23 15:00:00 to 01-SEP-23 19:00:00 (PST-8)
Location: EL CENTRO NAF
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

Westmorland Rd where it becomes Boley Rd was closed due to flooding. A bridge in the area was reportedly overtopped by water. The nearby West Main canal also experienced some washouts due to a large influx of water, per Imperial Irrigation District. No damages or injuries were reported.

Flash Flood in IMPERIAL, CALIFORNIA
From 01-SEP-23 13:40:00 to 01-SEP-23 16:40:00 (PST-8)
Location: OCOTILLO
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

Evan Hughes Hwy was closed due to considerable flooding between S2 and Dunaway Rd. No damages or injuries were reported. Timing estimated from radar.

Flash Flood in IMPERIAL, CALIFORNIA
From 01-SEP-23 14:40:00 to 01-SEP-23 19:40:00 (PST-8)
Location: NILAND
Flood cause: Heavy Rain
Property damage: 30.00M
Crop damage: 50.00K
Reported by: Department of Highways

Widespread 1 to 2 inches of radar estimated rain fell in Niland and areas just east into the Chocolate Mountains. A large area of considerable runoff flowed through Niland and the surrounding area, as evident in reports and before and after Sentinel2 satellite images, with upwards of 6 inches to 1 foot of flowing water in some areas, per photos and videos. Major flash flooding impacts were experienced. The East Highline Canal east of Niland, was overcome with flood waters and silt, mainly north of of Flowing Wells Rd. The overflowing canal was first reported a little after 1600PDT and only exacerbated the flooding. Several roads became impassable, unsafe, and subsequently closed due to flood water. At least a few cars became stuck in flood water leading to swift water rescues by land and air. The exact number of rescues is unknown. In Niland, several photos and videos showed flooded streets and yards, with water coming up to homes and businesses. There were a few reports of water entering homes, but it is unknown how many homes were impacted. Also impacted in the area was agriculture, as several fields had flood water moving through them. It is unknown the extent of any damages to the agricultural fields or the exact number. Sentinel2 satellite images showed evidence of all the disturbed earth, deposited mud and silt, through Niland, the agricultural fields and surrounding areas. In a statement by Imperial Irrigation District, the impacts to East Highline Canal resulted in a delay of 133 water deliveries. Also the O Lateral canal, which branches from East Highline canal, suffered structural damage. The main highway through the area, Hwy-111, was flooded in several locations, which hampered relief efforts. The small town of Slab City, to the northeast of Niland, was cut off from the rest of the Imperial Valley due to the flooded roads. As a result of the significant impacts, the County of Imperial issued an emergency proclamation for additional and better resources. Red Cross assisted in relief and a couple shelters for evacuees were established. There were no injuries reported from this event and specifics on property and crop damage is unknown and thus grossly estimated.

Flash Flood in RIVERSIDE, CALIFORNIA
From 01-SEP-23 16:00:00 to 01-SEP-23 20:00:00 (PST-8)
Location: DURMID
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

Hwy-111 was closed between the county line and North Shore due to several instances of flooded washes along the highway. No injuries or damages were reported.