California Extreme Heat Warning August 28: How to Protect Yourself Before the Evening Deadline

An Extreme Heat Warning is in effect right now across a broad swath of Southern California, covering more than a dozen distinct areas and remaining active until 8:00 PM MST on August 28, 2026. The warning was issued beginning at 1:56 PM MST on August 28, 2026, by the National Weather Service offices in Phoenix, AZ; San Diego, CA; and Los Angeles/Oxnard, CA. Affected zones include Joshua Tree National Park East, the Apple and Lucerne Valleys, the Coachella Valley, San Bernardino and Riverside County Valleys (the Inland Empire), the Santa Ana Mountains and Foothills, Orange County Inland, the Santa Clarita Valley, San Diego County Mountains, San Diego County Inland Valleys, the Santa Barbara County Southeastern and Southwestern Coasts, the Santa Ynez Mountains Western Range, and the Cuyama Valley. If you live, work, or are traveling through any of these areas, the time to adjust your plans is now.

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, requiring action to lessen the impact of the heat. That framing matters: this is not a routine warm afternoon. These are conditions that exceed what residents in these regions are typically prepared to handle.

If you must be outside, NWS guidance is direct: reschedule any strenuous activity to early morning or evening whenever possible, wear lightweight and loose-fitting clothing, and drink plenty of water. Knowing the signs and symptoms of heat exhaustion and heat stroke is not optional preparation for later. It is something you need to know before stepping outside right now.

For anyone working outdoors during this warning, the NWS specifically references guidance from the Occupational Safety and Health Administration: schedule frequent rest breaks in shaded or air-conditioned environments. This applies to construction crews, landscapers, delivery workers, and anyone else whose job puts them in direct sun during peak afternoon hours. If you or someone near you is overcome by heat, move them immediately to a cool, shaded location. Heat stroke is a medical emergency. Call 9-1-1.

Public cooling shelters are available in some areas covered by this warning. NWS advises consulting your county officials directly for shelter locations near you, as availability varies by jurisdiction. Do not wait until symptoms appear to find a cooling option. Identify the nearest shelter or air-conditioned space before you need it.

Why This Warning Connects to a Larger Pattern Worth Understanding

Extreme heat events across the American West have become one of the most consistent drivers of both public health emergencies and secondary infrastructure stress. The U.S. Department of Energy has taken visible steps in recent months to address grid reliability during peak demand periods, including actions to protect the Mid-Atlantic grid and ongoing work to strengthen energy reliability in Puerto Rico (see energy.gov for current federal initiatives). While this specific warning covers Southern California, it is a reminder that heat events place simultaneous strain on power grids, emergency services, and individual households across entire regions. At USRiskRadar, our evergreen guidance on heat preparedness, cooling center access, and household emergency planning is built precisely for situations like this one, where the official warning window is short but the preparation that makes the difference happens before the alert is ever issued. Bookmark your county emergency management page, know your nearest cooling shelter, and review your household heat plan while you still have time before the 8:00 PM MST expiration of this warning.

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 Los Angeles/Oxnard CA). Active alert data retrieved 2026-08-28 22:00 UTC via api.weather.gov.