A strong high pressure positioned over the Great Basin ushered in excessive temperatures into Southern California August 6-9. The desert areas and the Inland Empire experienced the hottest temperatures in this event. The inland areas experienced the brunt of the heat on August 6th-8th, with temperatures beginning to subside on August 9th. The coastal areas experienced their hottest temperatures on August 9th. The heat slowly began subsiding in all areas on August 10th, but remained quite hot throughout the week. Of significance, the Sea Surface Temperatures at La Jolla reached an all-time record high of 79.5F and several buoys reported 78-79F, peaking on August 9th. This is about 10 degrees above normal. The warm SST in July and August resulted in muggy conditions with dewpoints 70 to 72F reported for a few weeks at coastal observations including SAN. The minimum temperature did not drop below 70F at SAN for 36 consecutive days. Many days exceed 85F. August 2018 was the hottest on record for SAN (average temperature) and July and August combined was #2.

Heat in SAN BERNARDINO AND RIVERSIDE COUNTY VALLEYS - THE INLAND EMPIRE, CALIFORNIA
From 06-AUG-18 10:00:00 to 08-AUG-18 20:00:00 (PST-8)
Reported by: ASOS

The Inland Empire experienced temperatures in excess of 100 degrees on August 6th and 7th. Most areas in the Inland Empire experienced temperatures of 100-105 degrees, with the highest values observed in San Bernardino (108 degrees) and Lake Elsinore (111 degrees). The heat began to subside slightly on the 8th, with warm conditions continuing throughout the week.

Heat in COACHELLA VALLEY, CALIFORNIA
From 06-AUG-18 10:00:00 to 08-AUG-18 20:00:00 (PST-8)
Reported by: ASOS

The Coachella Valley experienced the most extreme temperatures in Southern California during this heat event. Thermal hit 117 degrees and Palm Springs reach 115 degrees on August 6th. Similar temperatures were observed on August 7th as well. Heat began to subside on Thursday, August 9th, but it remained quite warm in the Coachella Valley through the entire week.

Heat in APPLE AND LUCERNE VALLEYS, CALIFORNIA
From 06-AUG-18 10:00:00 to 08-AUG-18 20:00:00 (PST-8)
Reported by: ASOS

Apple and Lucerne Valleys experienced temperatures in excess of 100 degrees during this heat event. Apple Valley reached 106 degrees and Hesperia reached 107 degrees on August 6th. Temperatures dropped 3-4 degrees on August 7th, but still remained well above 100 degrees. Heat subsided slightly on August 8th and remained warm throughout the week.

Heat in ORANGE COUNTY INLAND, CALIFORNIA
From 06-AUG-18 10:00:00 to 09-AUG-18 20:00:00 (PST-8)
Reported by: ASOS

Orange County Inland areas experienced hot temperatures during this heat event, with most areas experiencing temperatures over 95 degrees. The highest temperatures were observed on August 9th, with Anaheim reaching 100 degrees and Santa Ana reaching 97 degrees. August 6th-8th had temperatures slightly lower, but still remained above 95 degrees. Temperatures began to subside on Friday August 10th, but remained over 90 degrees through the weekend.

Heat in SAN DIEGO COUNTY DESERTS, CALIFORNIA
From 06-AUG-18 10:00:00 to 08-AUG-18 20:00:00 (PST-8)
Reported by: ASOS

The San Diego County Deserts experience extreme temperatures on August 6th through 8th. Most areas experienced temperatures 100-105 degrees on August 6th, with similar temperatures observed on August 7th. Temperatures began to slowly subside on August 8th, but still remained over 95 degrees in most areas of the Lower Deserts. Heat slowly subsided throughout the week.

Heat in SAN DIEGO COUNTY VALLEYS, CALIFORNIA
From 06-AUG-18 10:00:00 to 08-AUG-18 20:00:00 (PST-8)
Reported by: ASOS

The San Diego County Valleys experienced temperatures in excess of 95 degrees in most areas from August 6th through August 9th. The warmest temperatures were observed on August 7th, with Valley Center reaching 103 degrees and Poway reaching 102 degrees. August 8th was not quite as hot, but still remained near 95 degrees in most areas. Hotter temperatures were observed on August 9th as well, with Ramona Airport reaching 103 degrees and Escondido reached 100 degrees. Heat began to subside on Friday, August 10th, but still remained quite warm throughout the weekend.

Heat in SAN DIEGO COUNTY MOUNTAINS, CALIFORNIA
From 07-AUG-18 10:00:00 to 07-AUG-18 20:00:00 (PST-8)
Reported by: ASOS

The San Diego County Mountains experienced temperatures in excess of 90 degrees on August 6th and 7th. Julian reached 91 degrees and Mount Laguna reached 89 degrees on August 6th. On August 7th, Julian reached 96 degrees and Mount Laguna reached 91 degrees. Heat subsided on Wednesday, August 8th, but still remained warm throughout the week.