LOS ANGELES, CA – Southern California entered what forecasters described as one of its most dangerous heat stretches of the year in late August, with temperatures expected to climb into the triple digits across much of the interior and reach as high as 112 degrees in some Los Angeles-area valleys.
The prolonged heat was driven by a strong ridge of high pressure dominating the region, bringing several consecutive days of unusually high temperatures, limited nighttime relief and elevated heat-related health risks.
By Aug. 24, the National Weather Service Los Angeles/Oxnard office had heat advisories in effect across broad portions of Los Angeles and Ventura counties, with the alerts scheduled to transition into more serious Extreme Heat Warnings beginning Tuesday morning.
The warnings were expected to remain in effect through 8 p.m. Friday, creating a multiday period in which residents would be exposed to potentially dangerous heat both during the afternoon and overnight.
NWS forecasters warned that temperatures could climb as high as 112 degrees in portions of the San Fernando Valley, San Gabriel Valley, Santa Clarita Valley, inland Ventura County and surrounding foothill and mountain communities.
“Heat related illnesses increase significantly during extreme heat events,” the National Weather Service said in its warning.
The agency urged residents to drink plenty of fluids, remain in air-conditioned environments whenever possible, avoid prolonged exposure to direct sunlight and check on relatives and neighbors who may be especially vulnerable.
Heat builds across Los Angeles County
The heat had already become noticeable by the beginning of the week.
Downtown Los Angeles was expected to approach the upper 90s, while several valley communities were forecast to climb well above 100 degrees.
The most serious conditions were expected Tuesday through Friday as the high-pressure system strengthened further.
The official NWS warning issued for portions of Los Angeles and Ventura counties called for temperatures of up to 112 degrees, replacing an earlier Heat Advisory that covered the first portion of the event.
The San Fernando Valley was among the areas facing the greatest exposure.
Communities including Woodland Hills, Northridge, Chatsworth, Van Nuys and Burbank were included in the warning area, along with Pasadena, Pomona, San Gabriel, Glendale and parts of the Santa Clarita Valley.
While individual temperatures could vary significantly depending on elevation and proximity to the coast, the broader pattern was clear: inland Southern California was entering several days of potentially dangerous heat.
Even areas that typically receive some marine influence were expected to run substantially warmer than normal.
Orange County also placed under extreme heat warning
The National Weather Service office in San Diego issued a separate Extreme Heat Warning for inland Orange County, covering communities including Santa Ana, Anaheim, Irvine, Orange, Fullerton, Garden Grove and Mission Viejo.
That warning was scheduled to run from 10 a.m. Tuesday through 8 p.m. Friday.
Forecasters expected inland Orange County highs generally in the mid-90s to around 104 degrees during the most intense portion of the heat wave.
Coastal communities were expected to remain cooler than the valleys and deserts, but even there, temperatures were forecast to rise above normal in many locations.
The difference between the coast and inland areas could be dramatic, with relatively moderate beach temperatures occurring at the same time that communities only a few dozen miles inland experienced dangerous triple-digit heat.
Desert heat already reaching dangerous levels
The desert had already demonstrated how intense the broader weather pattern could become.
At Palm Springs International Airport, the temperature reached 115 degrees on Aug. 23, according to an official National Weather Service climate report.
That was seven degrees above the normal maximum for the date, although still below the Palm Springs record of 119 degrees set in 1985.
The following day, Palm Springs recorded a maximum temperature of 107 degrees through 4 p.m., with an overnight minimum of 88 degrees, illustrating another major concern during prolonged heat waves: temperatures can remain extremely warm even after sunset.
Warm overnight lows prevent homes, pavement and the human body from cooling efficiently between hot afternoons.
That cumulative exposure can become especially dangerous when the heat persists for several consecutive days.
Overnight warmth increases health risks
Extreme heat becomes particularly hazardous when nights provide little relief.
Some valley communities were expected to remain in the 70s overnight, while desert locations could remain much warmer.
When nighttime temperatures stay elevated, buildings without effective air conditioning may retain heat through the night and become progressively hotter each day.
That can increase risks for older adults, infants and young children, people with chronic medical conditions, outdoor workers and residents without reliable access to air conditioning.
Los Angeles County identifies adults age 65 and older, young children, people who overexert themselves at work or during exercise and residents without adequate cooling as groups particularly vulnerable to heat-related illness.
The county’s Ready LA County heat program maintains an interactive map of public cooling centers available to residents seeking relief.
Most designated cooling centers provide air conditioning, drinking water and restrooms and are accessible to people with disabilities.
During especially severe heat events, some facilities may operate for extended hours as Augmented Cooling Centers.
Residents can also call 211 for information about cooling locations and other county resources.
Within the City of Los Angeles, residents can call 311 for additional information about heat-related services.
Outdoor workers face prolonged exposure
The extended heat also created concerns for thousands of people whose jobs require them to work outside or inside poorly cooled environments.
Construction crews, landscapers, agricultural workers, delivery drivers, street vendors and other employees may have limited ability to avoid the hottest hours of the afternoon.
As the heat intensified, Cal/OSHA issued a Southern California worker-safety advisory, noting that Extreme Heat Warnings covered portions of Los Angeles, Ventura, Santa Barbara, Riverside and San Bernardino counties.
The state agency specifically cited forecasts showing temperatures reaching 112 degrees in portions of Los Angeles, Ventura and Santa Barbara counties.
California employers are required to provide protections against heat illness.
For outdoor workers, those protections include sufficient drinking water, shade, preventative cool-down breaks and training on recognizing heat illness.
Indoor employers subject to California’s heat rules must similarly provide access to water and cool-down areas when workplace temperatures reach regulated thresholds.
The danger is not limited to obvious outdoor exposure.
Restaurants, warehouses, vehicle repair facilities, food trucks and other enclosed workspaces can become extremely hot when cooling systems are insufficient.
Heat illness can escalate rapidly
Heat exhaustion can begin with symptoms including heavy sweating, dizziness, fatigue, weakness, nausea and headache.
Heat stroke is a medical emergency.
Symptoms can include confusion, loss of consciousness and dangerously elevated body temperature.
Public health authorities advise calling 911 immediately if someone appears to be suffering from heat stroke.
Moving a person into shade or air conditioning and beginning efforts to cool the body can be critical while emergency personnel are on the way.
For people who must spend time outdoors, officials recommend carrying water, wearing lightweight clothing, using shade whenever possible and moving strenuous activity to the morning or evening.
The National Weather Service also advises never leaving children or pets unattended in vehicles.
Vehicle interiors can reach deadly temperatures quickly, even when the outside temperature is substantially lower than the highs expected during this heat wave.
Power outages add another risk
Extended periods of extreme heat can also place increased demand on the electrical system as millions of homes and businesses rely heavily on air conditioning.
Los Angeles County’s emergency preparedness guidance warns that power outages can occur during extreme heat and provides links for residents to check local utility outages.
An outage during a prolonged heat event can become more than an inconvenience.
Residents who rely on electrically powered medical equipment or refrigerated medication may need contingency plans, while people without power may need to relocate temporarily to a cooling center or another air-conditioned public facility.
County officials encourage residents to know where they can go before temperatures become dangerous.
Libraries, shopping centers and other air-conditioned public buildings may also provide temporary relief when dedicated cooling centers are not nearby.
Fire danger rises with temperatures
The same weather pattern creating the extreme heat also raised wildfire concerns.
The NWS Los Angeles/Oxnard office warned that portions of the region faced a high risk of fast-moving fires and extreme fire behavior if ignition occurred.
Very high temperatures accelerate moisture loss from grasses and other vegetation, creating increasingly dry fuels.
Forecasters urged people to use extreme caution with anything capable of producing a spark and to remain aware of surrounding conditions.
A major wind event was not initially expected to accompany the hottest portion of the heat wave, which reduced one traditional component of Southern California’s most dangerous fire-weather combinations.
However, extreme heat alone can still worsen fuel dryness and complicate firefighting operations if a fire begins.
By Aug. 25, Red Flag Warnings had appeared alongside Extreme Heat Warnings across parts of the NWS Los Angeles/Oxnard forecast area.
Monsoonal moisture could bring thunderstorms
Southern California’s mountains and deserts were also facing a small chance of thunderstorms as monsoonal moisture circulated into the region.
Forecast probabilities were generally low, but isolated thunderstorms can create localized hazards even during an otherwise widespread heat event.
Mountain or desert thunderstorms can produce brief heavy rain, gusty outflow winds and lightning.
Lightning becomes particularly concerning when vegetation is already extremely dry.
A thunderstorm does not necessarily provide lasting relief from extreme heat, and nearby areas can remain completely dry even when isolated rainfall develops.
The combination of intense heat, moisture and thunderstorms can also make conditions feel unusually muggy outside the desert.
Air quality can worsen during prolonged heat
Air quality was another concern during the extended hot weather.
Strong sunlight and high temperatures can accelerate chemical reactions that contribute to ground-level ozone, particularly across inland portions of the Los Angeles Basin.
That can create periods of unhealthy air even when smoke from wildfire is not present.
Children, older adults and people with asthma or other respiratory conditions can be particularly sensitive when ozone levels rise.
People can monitor regional conditions through the South Coast Air Quality Management District and limit strenuous outdoor activity when air quality deteriorates.
Poor air quality combined with extreme heat can create overlapping health risks, particularly for people who must remain outside for long periods.
Hottest stretch expected midweek
The most severe phase of the heat wave was expected Wednesday and Thursday.
Forecasts suggested downtown Los Angeles could approach 100 degrees, while several valley and foothill locations could reach between 106 and 112 degrees.
Inland Orange County was expected to reach the upper 90s and low 100s.
The Antelope Valley and Southern California deserts were expected to remain hotter still.
NWS alerts covering parts of Los Angeles County officially warned of temperatures up to 112 degrees through Friday.
That forecast represented more than a single unusually warm afternoon.
The prolonged duration meant residents could face four or more consecutive days of extreme conditions.
Forecasters consistently emphasize that duration matters because heat stress accumulates.
Someone who tolerates one hot afternoon may face much greater risk after several days of poor sleep, dehydration and continued exposure.
Relief expected after Friday
The heat was forecast to persist through Friday before a broader cooling trend began.
By Aug. 28 and 29, the Los Angeles/Oxnard National Weather Service office was telling residents that significant relief was expected from Saturday into Monday.
The change was expected to bring temperatures closer to seasonal levels after the prolonged period of dangerous heat.
Until then, officials continued urging Southern Californians to treat the event seriously.
For people with air conditioning, that meant limiting time outside during peak afternoon heat.
For people without reliable cooling, public facilities and cooling centers offered an alternative.
For employers, state rules required additional protections for workers.
And for families, officials emphasized checking regularly on elderly relatives, neighbors and anyone who might have difficulty recognizing or responding to heat illness.
Los Angeles County residents can find current cooling locations and heat-safety information through the county’s official excessive heat portal.
The National Weather Service’s warning was straightforward: with temperatures approaching 112 degrees in the hottest locations, heat-related illnesses could increase significantly, making access to water, shade and air conditioning especially important throughout the week.
