--- title: "Triple-digit heat returns to the valleys midweek, and the nights stay warm" description: "Valley highs stay in the 90s through Tuesday, then break 100 in the hottest spots Wednesday and Thursday. Forecasters put the odds of a long, dangerous stretch at about 80 percent. The detail that matters most for health is the overnight lows." category: "Los Angeles" category_url: https://herald.la/category/los-angeles author: "Omar Haddad" published: 2026-07-20T17:38:00.000Z updated: 2026-07-20T17:38:00.000Z canonical: https://herald.la/article/triple-digit-heat-returns-to-the-valleys-midweek-and-the-nights-stay-warm tags: ["heat", "weather", "public-health", "san-fernando-valley", "cooling-centers"] --- # Triple-digit heat returns to the valleys midweek, and the nights stay warm Valley highs stay in the 90s through Tuesday, then break 100 in the hottest spots Wednesday and Thursday. Forecasters put the odds of a long, dangerous stretch at about 80 percent. The detail that matters most for health is the overnight lows. The heat arrives midweek. Here is what the National Weather Service forecast, as carried in [local reporting](https://mynewsla.com/weather/2026/07/20/sweltering-heat-wave-coming-to-socal-this-week-3/), actually says, by area. ## The numbers Valley highs hold in the 90s through Tuesday. The hottest inland locations break 100 on **Wednesday and Thursday**, with the San Fernando, Santa Clarita and Antelope valleys carrying the highest readings. - **Lancaster**, in the Antelope Valley: around 103, easing to about 100. - **Van Nuys**, in the San Fernando Valley: around 101, then falling back into the 90s. - **Downtown Los Angeles**: mid-80s early in the week, about 91 on Thursday, 88 Friday, near 90 through the weekend. - **The coast**: substantially cooler, as usual. The marine layer is the reason the difference between Santa Monica and Woodland Hills in July can exceed 25 degrees. Accounts differ slightly on whether Wednesday or Thursday is the peak. Treat both as the hot days rather than planning around one. ## The part that actually matters The headline number is the daytime high. The number that determines whether people get hurt is the overnight low. From Thursday, valley lows are forecast to stay in the low to mid-70s. A house without air conditioning sheds heat overnight; when the night does not cool, it does not shed, and the following day starts from a higher baseline. Consecutive hot days with warm nights are what fills emergency rooms, not a single 103-degree afternoon. Forecasters put the chance of a long and dangerous heat wave, beginning as early as Wednesday and running through at least next weekend, at about 80 percent. That is a probability rather than a warning, and no excessive heat warning had been issued for the Los Angeles area as this was written. If one is issued, it will come from the Weather Service's Los Angeles/Oxnard office. There is also an enhanced risk of large fires away from the coast during the stretch. ## What to do **Cooling centers.** In Los Angeles County, call **211** at any hour to find the nearest one. Within the city of Los Angeles, **311** will also direct you. Public libraries are air-conditioned and open to anyone during normal hours, and do not require you to explain why you are there. **Check on people.** Older neighbors, people living alone, and anyone with heart or lung conditions or on medications that affect temperature regulation. A daily knock is the single most effective intervention there is. **Never leave a child or an animal in a car.** A parked car's interior climbs to lethal temperatures within minutes, including on days that do not feel extreme, and a cracked window does not meaningfully change it. **Outdoor workers.** California requires shade, water and rest breaks for outdoor workers when temperatures rise. Construction, landscaping, agriculture and delivery workers carry most of this region's heat risk, and they are the least able to reschedule. ## Knowing the difference [Heat exhaustion](https://heat.gov/tools-resources/warning-signs-and-symptoms-of-heat-related-illness/) looks like heavy sweating, cool and clammy skin, a fast weak pulse, nausea, dizziness and fatigue. Move the person somewhere cool, loosen clothing, give water in sips. **Heat stroke is a medical emergency.** The signs are a body temperature above about 103, skin that is hot and often dry, confusion or slurred speech, a strong rapid pulse, and possible loss of consciousness. The switch from sweating to not sweating is the dangerous transition. Call 911. Cool the person however you can while waiting, and do not give fluids to someone who is not fully alert. Heat kills more Americans in an average year than any other weather hazard, and it does it quietly, mostly indoors, mostly to people who were already vulnerable and alone. ## Sources - [Mid-week warmup to bring triple-digit heat back to SoCal](https://abc7.com/post/los-angeles-weather-temperatures-southern-california/58983/) - [Sweltering heat wave heads to SoCal](https://mynewsla.com/weather/2026/07/20/sweltering-heat-wave-coming-to-socal-this-week-3/) - [Buckle up, LA. This heat is going to be with us for a while](https://laist.com/news/climate-environment/la-july-heat-wave) - [Warning signs and symptoms of heat-related illness](https://heat.gov/tools-resources/warning-signs-and-symptoms-of-heat-related-illness/)