LOS ANGELES, CA – Southern California remained under a dangerous combination of extreme heat, elevated wildfire risk and possible preventive power shutoffs in late August, as temperatures climbed into the triple digits across inland communities and forecasters warned that the hottest part of the event could last through Friday.
The National Weather Service Los Angeles/Oxnard office had Extreme Heat Warnings and Red Flag Warnings in effect across parts of the region on Aug. 25, with officials warning residents to prepare for both heat illness and rapidly spreading fires if an ignition occurred.
The combination made this more than a routine summer heat wave.
Daytime temperatures were running well above normal, overnight temperatures were providing limited relief in many communities, vegetation was continuing to dry, and some inland areas were also facing gusty winds and very low humidity.
At the same time, Southern California Edison was monitoring high-fire-risk portions of its service territory for possible Public Safety Power Shutoffs, a preventive measure designed to reduce the chance that energized electrical equipment could start a wildfire during particularly dangerous weather.
Heat warnings stretch across Los Angeles County
The most widespread threat was extreme heat.
An official NWS warning for Los Angeles County’s inland coast, including downtown Los Angeles, called for temperatures as high as 102 degrees through 8 p.m. Friday.
That warning also covered communities including Hollywood, Beverly Hills, Culver City, Downey, Compton, Norwalk, Long Beach, Santa Monica, Malibu and Pacific Palisades.
Even traditionally cooler coastal areas were expected to experience unusually high temperatures.
The weather service warned that most coastal portions of Los Angeles, Ventura and southern Santa Barbara counties could see highs between 92 and 102 degrees, with warmer-than-normal overnight conditions reducing the amount of relief available after sunset.
Farther inland, conditions were substantially hotter.
Valleys, foothills and mountain-adjacent communities were expected to experience the most severe temperatures, with parts of the western San Fernando Valley and other interior areas potentially reaching around 106 to 112 degrees during the peak of the event.
Wednesday and Thursday were expected to represent the hottest portion of the heat wave before temperatures gradually began to ease.
The National Weather Service characterized the risk as significant even for otherwise healthy people who spend extended time outdoors.
“Heat related illnesses increase significantly during extreme heat events,” the agency said in its warning.
Residents were advised to drink plenty of fluids, remain in air-conditioned spaces when possible, avoid prolonged sun exposure and check on relatives and neighbors.
The agency also urged people to shift strenuous outdoor activity to early morning or evening hours.
Record heat already developing
The prolonged event had already begun producing unusually high temperatures by the beginning of the week.
Downtown Los Angeles reached the upper 90s, while other communities across Southern California were pushing toward or above the century mark.
The broader pattern was being driven by a strong ridge of high pressure that kept the region hot while allowing humidity to fall sharply in some interior locations.
Because the heat lasted for multiple days, forecasters were particularly concerned about warm nighttime temperatures.
Even when afternoon highs fall after sunset, homes and buildings without adequate air conditioning may remain hot for hours.
That cumulative exposure can increase heat stress over several consecutive days.
Older adults, young children, people with chronic illnesses, residents without reliable cooling and outdoor workers are especially vulnerable during prolonged heat events.
The NWS Los Angeles/Oxnard office described the episode as carrying a high risk for heat illness, particularly among sensitive groups.
Fire danger escalates as heat combines with dry air
The same atmospheric pattern also increased wildfire concerns.
A Red Flag Warning covered portions of the mountains and interior Los Angeles County as very hot temperatures combined with low humidity and locally gusty winds.
The NWS warned that if a fire started under those conditions, there was a high risk of rapid spread and extreme fire behavior.
Forecasters urged people to use extreme caution with anything capable of generating a spark and to remain alert to changing conditions, particularly in areas with high wildfire danger.
The fire threat was expected to be greatest away from the immediate coast.
Interior mountains, foothills and freeway corridors through northern Los Angeles County were among the areas of greatest concern.
High temperatures can dry vegetation more rapidly, while low humidity removes moisture from grasses, shrubs and other fuels.
When that happens alongside wind, even a relatively small ignition can become difficult to contain.
By Aug. 26, the NWS Los Angeles/Oxnard office was simultaneously displaying Extreme Heat Warnings, Red Flag Warnings and Wind Advisories across different portions of its forecast area.
Los Angeles fire agencies prepare for dangerous conditions
Fire agencies across the region were taking additional precautions as conditions deteriorated.
The Los Angeles Fire Department maintains a Red Flag program that can trigger parking restrictions in designated Very High Fire Hazard Severity Zones when wildfire conditions become particularly dangerous.
Those restrictions are designed to keep narrow roads, sharp curves and key evacuation routes clear for fire engines and residents who may need to leave quickly.
As of the afternoon of Aug. 25, LAFD said its Red Flag parking restrictions were not in effect, even though the broader region remained under fire-weather warnings.
That distinction matters because an NWS Red Flag Warning does not automatically mean City of Los Angeles Red Flag parking restrictions are activated.
The fire department makes its own determination based on local conditions.
Elsewhere in the county, fire departments can pre-position engines, hand crews and other resources closer to areas where an ignition would be especially difficult to control.
The goal is to reduce response times during weather periods when a small fire could grow rapidly.
Public Safety Power Shutoffs become another concern
Wildfire conditions also raised the possibility of preventive electricity shutoffs.
Southern California Edison uses Public Safety Power Shutoffs during extreme weather conditions when the risk of electrical equipment starting a fire becomes unusually high.
A PSPS is different from a conventional blackout.
Rather than electricity failing because of damaged equipment or excessive demand, the utility intentionally de-energizes selected circuits to reduce ignition risk.
SCE says roughly a quarter of its service territory is considered high fire risk, making wildfire-prevention measures a major part of its system planning.
During the late-August weather event, thousands of customers in high-fire-risk areas were being warned that they could potentially lose power if conditions became severe enough.
Areas under consideration included portions of the Santa Monica Mountains, Malibu-area communities, Castaic and northern Los Angeles County.
A warning does not mean a shutoff will definitely occur.
Utilities continue monitoring wind, humidity, vegetation conditions and equipment risk before making a final decision.
That means residents can receive advance notification and never actually lose electricity if weather conditions improve or remain below the utility’s shutoff threshold.
Why power can be cut during fire weather
Electrical equipment can become an ignition source when strong winds cause branches or debris to contact power lines or when damaged components fail.
During exceptionally dry conditions, a small spark can ignite vegetation and lead to a fast-moving wildfire.
PSPS programs are intended to reduce that possibility in the highest-risk areas.
However, shutoffs carry their own consequences.
People may lose air conditioning during extreme heat, businesses can lose refrigeration and electronic payment systems, and medically vulnerable residents may depend on electrically powered equipment.
That tension becomes especially serious when wildfire weather and extreme heat occur at the same time.
A preventive power outage during a 100-degree day can create an immediate health problem for residents who cannot relocate to a cooler location.
SCE therefore encourages customers in fire-prone areas to maintain emergency plans and monitor utility notifications during periods of dangerous weather.
Air quality also deteriorates
Heat was not the only environmental concern.
The South Coast Air Quality Management District issued an air quality alert for harmful ozone pollution across portions of the Los Angeles Basin during the heat wave.
The NWS alert covered areas including the San Fernando Valley, San Gabriel Valley, Santa Clarita Valley, downtown Los Angeles and nearby foothills.
Ozone can build more readily during intense sunlight and high temperatures.
Children, older adults and people with asthma or other respiratory illnesses may experience greater effects when ozone reaches unhealthy levels.
Residents can monitor conditions through the South Coast AQMD.
During periods of poor air quality, sensitive groups may need to limit strenuous outdoor activity even if they can otherwise tolerate the heat.
Beach areas bring a different hazard
For residents trying to escape inland heat by heading toward the coast, the weather created another concern.
The National Weather Service issued a Beach Hazards Statement for portions of the Los Angeles County coast, Malibu and Ventura County because of dangerous rip currents and elevated surf.
The agency warned that rip currents could pull swimmers and surfers away from shore and that breaking waves could create hazardous swimming conditions.
People who entered the water were advised to remain near occupied lifeguard towers.
That meant the coast offered somewhat cooler temperatures but was not free of weather-related hazards.
Heat and fire danger overlap
The combination of heat, low humidity, gusty winds and dry vegetation created a particularly difficult risk profile.
Normally, people are encouraged to escape extreme heat by staying indoors with air conditioning.
But in high-fire-risk areas, a PSPS can remove that option.
Similarly, residents may consider heading toward beaches, only to encounter hazardous surf and rip-current conditions.
Wildfire smoke, if a significant fire begins, can further complicate conditions by degrading air quality.
Emergency agencies therefore encouraged residents to prepare for multiple possible hazards rather than focusing solely on the temperature.
A timeline for the week
The most intense period was expected to unfold through Friday.
Tuesday marked the beginning of the most dangerous combination of heat and fire conditions as Red Flag Warnings and expanded Extreme Heat Warnings took effect.
Wednesday and Thursday were forecast to bring the highest temperatures across many inland communities.
Friday was expected to remain hot, although temperatures were projected to begin easing slightly.
The NWS maintained the Extreme Heat Warning for many Los Angeles-area communities until 8 p.m. Friday.
By Aug. 28, the weather service was forecasting a significant cooldown from Saturday through Monday.
That relief would reduce both heat stress and some of the fire-weather pressure that had built throughout the week.
Residents urged to prepare for heat and outages
Health and emergency officials continued recommending several basic precautions.
Residents should drink water regularly, spend time in air-conditioned environments, avoid strenuous afternoon activity and check on older neighbors or relatives.
Children and pets should never be left inside parked vehicles.
People living in areas vulnerable to PSPS events should also keep phones and battery packs charged, know where they can relocate if power is shut off and have a plan for medications or medical devices requiring electricity.
People who see smoke or fire should call 911 immediately.
Because PSPS decisions can change quickly, customers in SCE territory should use the utility’s wildfire safety and outage resources for current information rather than assuming that an advance warning means electricity will definitely be shut off.
