Temperatures will rise well above triple digits across much of Southern California, and the warmest days of the week are upon us.

Temperatures will reach triple digits in the valleys and inland by Friday. For the rest of the week, highs of 95 to 105 degrees are expected in the Los Angeles basin and above 80 degrees on the coast.

Temperatures have been rising by a few degrees each day this week. Highs of over 95 degrees are expected in the Los Angeles basin by Wednesday. Temperatures will spread into the valleys by Thursday.

In the valleys, night temperatures will remain above 20 degrees this week.

Highs in the interior are expected to be between 40 and 43 degrees. In some parts of the Inland Empire and San Fernando Valley, temperatures could reach as high as 44 degrees.

A heat warning for all of Southern California, except for coastal communities, begins Wednesday and lasts through Friday. Thursday and Friday will be the warmest days of the week, with temperatures 10 to 15 degrees above average.

“Dangerous heat is on the way, and it will stay like this, if not hotter, for the next three days,” said NBCLA meteorologist Shanna Mendiola. “We’re not getting a break overnight. These warm lows are going to stick with us for the next few nights.”

The hot and dry weather in the mountains, valleys and deserts will be accompanied by an increased risk of forest fires.

The South Coast Air Quality Management District has issued an ozone warning that will remain in effect until 8 p.m. Friday as elevated smog levels are expected due to the heat wave. According to the AQMD, ozone levels in the Santa Clarita Valley and parts of the San Gabriel Valley are expected to reach health-threatening levels or higher by Friday.

“It’s going to be very hot,” Mendiola said. “The heat will boil up some of the ozone. What is ozone? It’s a type of pollution that we have in the air. The heat isn’t going to make it any better. There might be some haze outside, and that’s an indication that the air quality isn’t the best.”

Click here for cooling centers in Los Angeles County.

A heat warning is in effect across Southern California as temperatures continue this week. Annette Arreola reports for NBC4 News at 6 a.m. on September 4, 2024.

Tips for keeping a cool head in hot weather

Scroll for tips on how to stay cool this week.

• Stay hydrated! The more fluids you drink, the better your body will be at keeping you cool. Drink water – not carbonated or alcoholic drinks, which will dehydrate you.
• Avoid physical activity during the midday hours. If you must exercise outside, do so early in the morning when temperatures are lower.
• Wear light, bright natural fabrics like cotton and linen as these allow your skin to breathe and allow your sweat to evaporate, cooling you down.
• We sweat about half a litre a day on both feet (and we wonder why they stink!), so if possible, wear sandals or flip-flops to allow foot sweat to evaporate.
• Use a fan to circulate air from open windows. Keep blinds or curtains closed during the day to prevent your home from heating up while you’re away. Turn off large appliances and prevent power outages!
• To cool down quickly, hold your wrists under a cold faucet or keep a water spray bottle in the refrigerator to give your face a quick, cooling spritz.
• Keep some wet wipes in your bag so you can freshen your hands, face and neck when you feel hot or clammy.
• Want to stay cool at night? One option is to wash your feet in cold water or take a cold shower before bed – especially if you get hot or sweat a lot at night.
• To keep cool in bed, store your pillowcase or sheets in a plastic bag in the refrigerator during the day. Put them back on the bed at night. The fabric will stay cool when you’re ready to go to sleep.
• And bring your pets inside and make sure they have shade and water.
• Be prepared for power outages and know where cooling centers are located!