A long duration heat wave impacted inland portions of Southern California July 7 to 29 with nearly continuous warnings and advisories. San Diego County public health reported 224 heat related incidents around their network of 23 hospitals. Numerous record highs were broken in the lower deserts where temperatures topped 115 for many days in a row, as well as across the inland valleys and mountains. Overnight low temperatures remained elevated in the lower deserts as lows only fell into the mid-80s to mid-90s, exacerbating the extreme heat risk.
July 2023 was the hottest month on record at Palm Springs.

Excessive Heat in COACHELLA VALLEY, CALIFORNIA
From 11-JUL-23 09:00:00 to 22-JUL-23 19:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

A long-duration, excessive heat wave impacted the Coachella Valley from July 11-22. Highs in the lower deserts generally ranged from 110-120 each day, with the highest temperatures occurring on Thursday, July 20 and Friday, July 21. The following are the highest temperatures recorded through the event, and the days on which they occurred:
Palm Springs AP: 120 (7/21/23); Palm Springs ranged from 113-120 through the duration of the event, with overnight lows of 83-93 degrees each day. Palm Springs broke a high temperature record of 119 (7/20), breaking the previous record of 118, and 120 (7/21), tying the previous record of 120.
Indio: 119 (7/20/23); Indio ranged from 111-119 through the duration of the event, with overnight lows of 90-96 degrees each day. Indio broke a highest minimum temperature record at 94 (7/18), breaking the previous record of 91. Indio broke a high temperature record of 119 (7/20), breaking the previous record of 117, and 118 (7/21), breaking the previous record of 117.
Thermal Airport: 118 (7/20/23 and 7/21/23) Thermal ranged from 111-118 through the duration of the event, with overnight lows of 77-93 degrees each day. Thermal broke a highest minimum temperature record at 89 (7/13), breaking the previous record of 88, at 92 (7/18), breaking the previous record of 86. Thermal broke a high temperature record of 117 (7/20), breaking the previous record of 115.

Excessive Heat in SAN DIEGO COUNTY MOUNTAINS, CALIFORNIA
From 14-JUL-23 09:00:00 to 22-JUL-23 19:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: RAWS

A long-duration, excessive heat wave occurred across the San Diego County Mountains from July 14-22. Highs reached the 90s each day. The following are the highest temperatures reported during the event, and the day on which the peak temperature occurred:
Julian: 99 (7/15/23) Julian ranged from 89-99 through the duration of the event, with overnight lows of 64-74 degrees each day.
Lake Cuyamaca: 96 (7/15/23 & 7/22/23) Lake Cuyamaca ranged from 86-96 through the duration of the event, with overnight lows of 65-71 degrees each day.
Mount Laguna: 93 (7/21/23) Mount Laguna ranged from 86-93 through the duration of the event, with overnight lows of 63-67 degrees each day.

Excessive Heat in SAN DIEGO COUNTY DESERTS, CALIFORNIA
From 11-JUL-23 09:00:00 to 22-JUL-23 19:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

A long-duration, excessive heat wave impacted the San Diego County Deserts from July 11-22. Highs in the lower deserts generally ranged from 110-120 each day, with the highest temperatures occurring on Thursday, July 20 and Friday, July 21. The following are the highest temperatures recorded through the event, and the days on which they occurred:
Borrego Springs: 117 (7/21/23) Borrego Springs ranged from 109-117 through the duration of the event, with overnight lows of 82-91 degrees each day.
Ocotillo Wells: 121 (7/20/23)Ocotillo Wells ranged from 113-121 through the duration of the event, with overnight lows of 87-98 degrees each day.

Excessive Heat in RIVERSIDE COUNTY MOUNTAINS, CALIFORNIA
From 14-JUL-23 09:00:00 to 22-JUL-23 19:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: RAWS

A long-duration, excessive heat wave occurred across the Riverside County Mountains from July 14-22. Highs reached the upper-80s and 90s each day, with a few days topping 100 degrees. The following are the highest temperatures reported during the event, and the day on which the peak temperature occurred:
Idyllwild: 100 (7/15/23) Idyllwild ranged from 90-100 through the duration of the event, with overnight lows of 58-66 degrees each day. Idyllwild broke a high temperature record at 100 (7/15), breaking the old record of 97.
Anza: 104 (7/15/23) Anza ranged from 95-104 through the duration of the event, with overnight lows of 59-69 degrees each day.

Excessive Heat in SAN BERNARDINO COUNTY MOUNTAINS, CALIFORNIA
From 14-JUL-23 09:00:00 to 22-JUL-23 19:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

A long-duration, excessive heat wave occurred across the San Bernardino County Mountains from July 14-22. Highs reached the 80s and 90s each day. A brief lull in the heat occurred July 18-20 before ramping back up on July 21.  The following are the highest temperatures reported during the event, and the day on which the peak temperature occurred:
Lake Arrowhead: 97 (7/15/23) Lake Arrowhead ranged from 90-97 through the first half of the event, reaching the upper-80s to low-90s again by the 21st.
Big Bear Lake: 92 (7/15/23) Big Bear Lake ranged from 85-92 through the first half of the event, reaching the upper-80s again by the 21st.
Big Bear City: 90 (7/15/23) Big Bear City ranged from 86-90 through the first half of the event, reaching the upper-80s again by the 21st.
Baldwin Lake: 95 (7/16/23) Baldwin Lake ranged from 90-95 through the first half of the event, reaching the low-90s again by the 21st.

Excessive Heat in SANTA ANA MOUNTAINS AND FOOTHILLS, CALIFORNIA
From 14-JUL-23 09:00:00 to 22-JUL-23 19:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: RAWS

A long-duration, excessive heat wave occurred across the Santa Ana Mountains from July 14-22. Highs reached the upper-90s to near 100 degrees each day. The following are the highest temperatures reported during the event, and the day on which the peak temperature occurred:
El Cariso: 100 (7/20/23) El Cariso ranged from 95-100 through the duration of the event, with overnight lows of 72-79 degrees each day.

Excessive Heat in APPLE AND LUCERNE VALLEYS, CALIFORNIA
From 13-JUL-23 09:00:00 to 22-JUL-23 19:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: RAWS

A long-duration, excessive heat wave occurred across the High Desert from July 12-22. Highs reached the mid-90s to upper-100s each day. A brief downtrend in the highs occurred July 17-20 before ramping back up on July 21. The following are the highest temperatures reported during the event, and the day on which the peak temperature occurred:
Hesperia: 106 (7/15/23) Hesperia ranged from 102-106 through the first half of the event, with highs reaching the low-100s again by July 21.
Apple Valley: 110 (7/15/23) Anza ranged from 100-110 through the duration of the event.

Excessive Heat in SAN BERNARDINO AND RIVERSIDE COUNTY VALLEYS - THE INLAND EMPIRE, CALIFORNIA
From 11-JUL-23 09:00:00 to 22-JUL-23 19:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

A long-duration, excessive heat wave occurred across the Inland Empire from July 11-22. Highs reached the 90s and 100s each day. The following are the highest temperatures reported during the event, and the day on which the peak temperature occurred:
San Bernardino AP: 104 (7/15/23 and 7/16/23) San Bernardino AP ranged from 99-104 through the duration of the event, with overnight lows of 68-74 degrees each day.
Ontario AP: 100 (7/17/23, 7/19/23, 7/20/23) Ontario AP ranged from 94-100 through the duration of the event, with overnight lows of 67-72 degrees each day.
March ARB: 103 (7/15/23) March ARB ranged from 97-103 through the duration of the event, with overnight lows of 63-75 degrees each day.
Riverside AP: 103 (7/20/23) Riverside AP ranged from 97-103 through the duration of the event, with overnight lows of 67-73 degrees each day.
San Jacinto: 106 (7/15/23) San Jacinto ranged from 98-106 through the duration of the event, with overnight lows of 68-74 degrees each day. San Jacinto broke a high minimum temperature record at 74 (7/17), breaking the previous record of 73.
Lake Elsinore: 104 (7/15/23, 7/16/23, 7/20/23) Lake Elsinore ranged from 98-104 through the duration of the event, with overnight lows of 66-72 degrees each day.

Excessive Heat in SAN DIEGO COUNTY VALLEYS, CALIFORNIA
From 11-JUL-23 09:00:00 to 22-JUL-23 19:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

A long-duration, excessive heat wave occurred across the San Diego County Valleys from July 11-22. Highs reached the upper-80s and 90s each day, with a few locations topping 100 degrees. The following are the highest temperatures reported during the event, and the day on which the peak temperature occurred:
Ramona AP: 100 (7/20/23) Ramona AP ranged from 93-100 through the duration of the event, with overnight lows of 58-67 degrees each day.
Santee: 100 (7/17/23) Santee ranged from 87-100 through the duration of the event, with overnight lows of 62-68 degrees each day.
San Pasqual Valley: 100 (7/17/23) San Pasqual Valley ranged from 90-100 through the duration of the event, with overnight lows of 56-66 degrees each day.
Valley Center: 100 (7/17/23) Valley Center ranged from 93-100 through the duration of the event, with overnight lows of 60-69 degrees each day.
Rancho Bernardo: 90 (7/15/23) Rancho Bernardo ranged from 81-90 through the duration of the event, with overnight lows of 63-66 degrees each day.
Alpine: 98 (7/17/23) Alpine ranged from 89-98 through the duration of the event, with overnight lows of 62-72 degrees each day.

Excessive Heat in ORANGE COUNTY INLAND, CALIFORNIA
From 11-JUL-23 09:00:00 to 20-JUL-23 00:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Hot conditions occurred across inland Orange County Valleys from July 10-14. Highs reached the upper-80s and 90s each day. The following are the highest temperatures reported during the first portion of the event, and the day on which the peak temperature occurred:
Yorba Linda: 96 (7/12/23, 7/14/23). Yorba Linda ranged from 93-96 through the duration of the event.
Fullerton AP: 93 (7/12/23). Fullerton ranged from 89-93 through the duration of the event.
Santa Ana: 92 (7/12/23). Santa Ana ranged from 86-92 through the duration of the event.
Anaheim tied the record (1990) of 97 degrees on July 13.
After a brief cooldown on July 15 and July 16, temperatures rose again July 17-20. The following are the highest temperatures reported during the second half of the event, and the day on which the peak temperature occurred:
Yorba Linda: 98 (7/19/23, 7/20/23). Yorba Linda ranged from 96-98 through the duration of the event.
Fullerton AP: 93 (7/19/23). Fullerton ranged from 89-93 through the duration of the event.
Santa Ana: 91 (7/19/23, 7/20/23). Santa Ana ranged from 90-91 through the duration of the event.
Anaheim tied the record of 96 degrees on July 17 (2006) and again on July 18 (1992), and tied the record of 98 (2016) on July 20.