California Extreme Heat Warning Through August 28: How to Work Outside Safely and Find Cooling Shelters Now

An Extreme Heat Warning is in effect across a wide swath of Southern California, covering areas from the Coachella Valley and Joshua Tree National Park East to the San Bernardino and Riverside County Valleys, also known as the Inland Empire. The warning, issued by the National Weather Service offices in Phoenix, San Diego, Hanford, and Los Angeles/Oxnard, became effective August 25, 2026 at 12:57 PM MST and runs through August 28, 2026 at 8:00 PM MST.

Additional areas under this warning include San Diego County Inland Valleys, San Diego County Mountains, Apple and Lucerne Valleys, Santa Ana Mountains and Foothills, Orange County Inland, Indian Wells Valley, Catalina and Santa Barbara Islands, and the Cuyama Valley. That is a large geographic footprint, spanning coastal-adjacent communities, desert valleys, and mountain foothills alike.

What the National Weather Service Is Telling You to Do Right Now

The National Weather Service defines an Extreme Heat Warning as a period of very hot temperatures, even by local standards. The agency is clear: actions should be taken now to lessen the impact. This is not a passive watch or an advisory. If you live or work in any of the listed areas, the NWS expects you to change your behavior through the duration of this warning.

If you work or spend time outdoors, reschedule any strenuous activity to early morning or evening hours whenever possible. When you must be outside, wear lightweight, loose-fitting clothing and drink plenty of water consistently, not just when you feel thirsty.

For outdoor workers specifically, the Occupational Safety and Health Administration guidance cited directly in this alert calls for scheduling frequent rest breaks in shaded or air-conditioned environments. Employers and workers in agriculture, construction, landscaping, and similar fields should treat this as a workplace safety requirement, not optional guidance.

Know the difference between heat exhaustion and heat stroke. Heat stroke is a medical emergency. If someone near you becomes confused, stops sweating, or loses consciousness in the heat, call 911 immediately and move them to a cool, shaded location while you wait for help.

Public cooling shelters are available in some areas covered by this warning. Contact your county officials directly to find the nearest open location. This resource matters most for people without reliable air conditioning at home, including renters in older buildings, individuals experiencing homelessness, and those caring for elderly family members.

Why This Warning Fits a Larger Pattern Worth Preparing For

Fire remains the leading driver of federal disaster declarations in recent months, with 35 of the last 54 federal declarations tied to fire events, concentrated heavily in Western states including California, according to federal emergency management data. Extreme heat and fire risk are not always the same event, but they share the same seasonal window and the same underlying conditions: low humidity, high temperatures, and stressed infrastructure. Heat events like this one are also the moments when power grids face their highest demand, and when a grid disruption compounds every other risk. The U.S. Department of Energy has flagged grid reliability as an active concern, with the Energy Secretary taking steps to protect regional transmission capacity (energy.gov). Building a household preparedness baseline now, before a compounding event, is the practical takeaway from any alert like this one.

Check back at USRiskRadar.com as this warning progresses through August 28. If conditions in your area change, the issuing NWS offices will update or extend the alert, and we will reflect those changes here.

For the fundamentals that apply beyond this specific alert, see our Extreme Heat Preparedness guide.

Source: National Weather Service (NWS Phoenix AZ, NWS San Diego CA, NWS Hanford CA, NWS Los Angeles/Oxnard CA). Active alert data retrieved 2026-08-25 22:00 UTC via api.weather.gov.