An Extreme Heat Warning is in effect right now across a wide swath of Southern California, covering areas from the Coachella Valley to the Santa Ana Mountains and from the San Diego County Inland Valleys to the Catalina and Santa Barbara Islands. The warning, issued by the National Weather Service offices in San Diego, Hanford, and Los Angeles/Oxnard, became effective on August 24, 2026, at 2:08 PM PDT and runs through August 28, 2026, at 8:00 PM PDT.
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The full list of areas under this warning, as designated by the National Weather Service, includes: Orange County Inland; Santa Ana Mountains and Foothills; San Diego County Inland Valleys; Coachella Valley; San Diego County Mountains; San Bernardino and Riverside County Valleys (the Inland Empire); Apple and Lucerne Valleys; Indian Wells Valley; Catalina and Santa Barbara Islands; Santa Clarita Valley; Western Antelope Valley Foothills; and Cuyama Valley. If you or anyone you know lives or works in any of these zones, the guidance below applies directly to you.
What NWS Is Telling Residents to Do Right Now
The National Weather Service San Diego CA, the lead issuing office, has provided clear and specific instructions for anyone in the affected areas. Those instructions are worth reading word for word: drink plenty of fluids, stay in an air-conditioned room, stay out of the sun, and check up on relatives and neighbors.
Each of those four points carries real weight during a multi-day extreme heat event. Fluid intake is not a background task; it needs to be deliberate and consistent, even if you do not feel thirsty. Air conditioning is not a comfort measure during a warning like this, it is the primary protective environment. If your home does not have reliable cooling, the NWS instruction to stay in an air-conditioned room points directly toward using a public cooling center, a library, or a shopping center until conditions ease.
Staying out of the sun is especially critical during the peak afternoon hours, when radiant heat compounds the ambient air temperature and significantly increases the risk of heat illness. Plan any necessary outdoor activity for early morning if it cannot be postponed entirely.
The instruction to check up on relatives and neighbors is not a courtesy reminder. It is an operational step. Elderly residents, young children, people with chronic medical conditions, and anyone without access to air conditioning face the highest risk during a multi-day heat event. A phone call or a brief visit can be the difference between a manageable situation and a medical emergency. Do not assume someone is fine because you have not heard otherwise.
Why Multi-Day Heat Events Demand a Preparedness Mindset
This warning runs nearly four full days, from the afternoon of August 24 through the evening of August 28. That duration matters because the body’s ability to recover from heat stress depends on nighttime temperatures dropping enough to allow cooling. When a heat event stretches across multiple days and nights, cumulative stress builds even in people who felt fine on day one. At usriskradar.com, our year-round guidance on heat preparedness centers on exactly this pattern: the highest-risk moment of a multi-day event is often not the first afternoon but the second or third day, when fatigue, dehydration, and disrupted sleep compound together. Reviewing your household’s heat plan now, confirming that your cooling systems are working, identifying the nearest public cooling resource, and building a check-in routine with vulnerable people in your network are the actions that make the four official NWS steps above sustainable across the full warning period.
Monitor updates directly from the National Weather Service at weather.gov and from your local NWS office as conditions develop through August 28.
For the fundamentals that apply beyond this specific alert, see our Extreme Heat Preparedness guide.
Source: National Weather Service (NWS San Diego CA, NWS Hanford CA, NWS Los Angeles/Oxnard CA). Active alert data retrieved 2026-08-24 22:00 UTC via api.weather.gov.
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