--- title: "Another heat wave lands Wednesday, with a warning that the nights stay warm" description: "The National Weather Service has a heat advisory up from 10 a.m. Wednesday through Monday. Inland valleys run to about 105, the coast into the low-to-mid 90s, the beaches in the upper 70s. Humidity keeps the overnight lows high, and the surf is dangerous. It is the second advisory in barely a week." category: "Los Angeles" category_url: https://herald.la/category/los-angeles author: "Hana Nakamura" published: 2026-07-21T23:28:00.000Z updated: 2026-07-21T23:28:00.000Z canonical: https://herald.la/article/another-heat-wave-lands-wednesday-and-a-warning-that-the-nights-stay-warm tags: ["heat", "weather", "public-health", "beaches", "southern-california"] --- # Another heat wave lands Wednesday, with a warning that the nights stay warm The National Weather Service has a heat advisory up from 10 a.m. Wednesday through Monday. Inland valleys run to about 105, the coast into the low-to-mid 90s, the beaches in the upper 70s. Humidity keeps the overnight lows high, and the surf is dangerous. It is the second advisory in barely a week. Here comes another one. The National Weather Service has issued a heat advisory for much of Southern California running from 10 a.m. Wednesday through Monday, [LAist reports](https://laist.com/news/climate-environment/another-socal-heat-wave-could-last-awhile), less than a week after the last one lifted. ## The numbers, by area The forecast, as with any Southland heat event, is really several forecasts depending on how far you are from the ocean. - **Inland valleys** (the San Fernando and San Gabriel valleys, and Riverside and San Bernardino counties): mid-90s up to about 105. - **The coast**, including downtown Los Angeles and much of Orange County: low to mid-90s. - **The beaches**: upper 70s. Temperatures build over Wednesday and Thursday. Because this is a multi-day advisory rather than a one-afternoon spike, the effect accumulates. ## The number that matters most As with the last heat wave, the daytime high is not the figure to watch. It is the overnight low. Humidity is expected to persist through this event, and humid nights do not cool off. A home without air conditioning sheds its heat after dark; when the air stays warm and damp, it sheds less, and the next day starts hotter. Several consecutive hot days with warm, muggy nights are what actually harm people, because the body never gets the overnight recovery it depends on. That is why an advisory that runs Wednesday to Monday is more serious than its peak temperature suggests. The danger is the duration. ## Who is at risk, and the water The people most exposed are the familiar ones: those without air conditioning, outdoor workers, older adults, and young children. Check on the neighbors who fit those descriptions, daily, for the length of the advisory. This event comes with a second hazard that the last one did not emphasize. Large waves and strong rip currents are expected at the beaches through the weekend. That combination, a heat wave driving crowds to the coast at the same time the surf turns dangerous, is a specific and predictable risk. If you go to the water to escape the heat, swim near a lifeguard, and take a rip current seriously: it pulls you out, not under, and the move is to swim parallel to the shore until you are out of it rather than fighting straight back in. There is also elevated fire risk in the drier corridors away from the coast, as there is in any prolonged heat. ## The line worth repeating The forecasters make a point that is easy to skip past, and the Herald will not: heat waves are getting hotter, longer and more frequent as the climate warms. A second advisory inside of a week is not, by itself, proof of anything, but it is consistent with the trend the science describes. The practical response is unchanged from the last time we ran it. Stay ahead of the heat rather than reacting to it: drink water before you are thirsty, do the strenuous outdoor work early or late, never leave a child or an animal in a car, and know where a cooling center is. In Los Angeles County, calling 211 will find the nearest one. ## Sources - [Brace for another SoCal heat wave. This one could last awhile](https://laist.com/news/climate-environment/another-socal-heat-wave-could-last-awhile)