A very strong upper level high pressure became positioned over California along with an offshore flow in Southern California resulting in record very hot temperatures. September 5th and 6th were the hottest and several all-time highs were broken. The Valley and the El Dorado wildfires also started on Saturday September 5th, which scorched parts of the mountains.

Wildfire in SAN BERNARDINO COUNTY MOUNTAINS, CALIFORNIA
From 05-SEP-20 10:40:00 to 30-SEP-20 10:00:00 (PST-8)
Crop damage: 0.00K
Reported by: Park/Forest Service

The El Dorado wildfire started at approximately 10:40 AM on September 5th, scorching 22,680 acres over a 23 day period into parts of the San Bernardino and Riverside County Mountains. The fire forced road closures (including State Highway 38) and the evacuations of Oak Glen, north Yucaipa, Mountain Home Village, Forest Falls, and Angelus Oaks communities. There were 4 residences damaged, 5 residences destroyed along with 15 other structures destroyed. 13 firefighters were injured as well as one fatality while fighting the flames. The fire is expected to be fully contained by mid-December. CalTrans started repairing the road and surrounding areas in early October and expects the project to be completed by late Spring 2021.

Excessive Heat in SAN BERNARDINO AND RIVERSIDE COUNTY VALLEYS - THE INLAND EMPIRE, CALIFORNIA
From 05-SEP-20 08:00:00 to 06-SEP-20 20:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

High temperatures across the Inland Empire ranged from 110 to over 120 degrees for this event. The Riverside ASOS reported 117 degrees on the 5th and 6th, breaking two daily record highs. The Chino ASOS reported 121 degrees on the 6th, making it the hottest temperature ever recorded in the Inland Empire.

Excessive Heat in SAN DIEGO COUNTY VALLEYS, CALIFORNIA
From 05-SEP-20 08:00:00 to 06-SEP-20 20:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Parts of the area rose up to 110 to 115 degrees during this time period. The Ramona ASOS broke two daily record highs on the 5th and 6th, reaching 112 degrees each day.
Escondido had an all-time high of 115��F. On September 6th, an all-time high of 113 was recorded at Alpine on September 5th. San Diego county Public Health recorded significant (77) hospitalizations due to the excessive heat.

Excessive Heat in COACHELLA VALLEY, CALIFORNIA
From 04-SEP-20 08:00:00 to 06-SEP-20 20:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Very hot temperatures were experienced in parts of the Coachella Valley with temperatures 115 to over 120 degrees. The Palm Springs ASOS recorded 3 daily high temperatures records on the 4th, 5th and 6th of the month with the highest reaching 122 degrees, one degree shy of the all time record high.

Excessive Heat in APPLE AND LUCERNE VALLEYS, CALIFORNIA
From 04-SEP-20 08:00:00 to 07-SEP-20 20:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: RAWS

Hot temperatures from 100 to 110 degrees were reported across areas of the high desert from the 4th to the 7th.

Wildfire in SAN DIEGO COUNTY MOUNTAINS, CALIFORNIA
From 05-SEP-20 14:30:00 to 24-SEP-20 10:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Fire Department/Rescue

The Valley Fire started on September 5th at approximately 2:30 PM and burned approximately 16,390 acres across the southern portion of the San Diego County Mountains until being 100% contained on September 24th. Many resources were deployed with some parts of the area having evacuation orders issued.

Excessive Heat in SAN DIEGO COUNTY DESERTS, CALIFORNIA
From 04-SEP-20 08:00:00 to 07-SEP-20 20:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Parts of the lower deserts reported highs above 110 degrees during this time period. The peak of the heat was on the 5th and 6th, where some areas hit close to the 120 degree mark. Anza Borrego State Park broke daily record highs on the 5th and 6th, reaching 117 degrees both days.