Southern California weather: Triple-digit heat triggers extreme heat, Red Flag Warnings

LOS ANGELES - Southern California is experiencing its most intense heat wave of the year this week as a high-pressure system pushes temperatures well into the triple digits across valleys, mountains, and desert communities. 

Public health and weather officials have issued urgent safety warnings as dangerous heat, elevated humidity, and critical fire risks threaten the region through Thursday evening.

What we know:

Extreme heat warnings from the National Weather Service (NWS) are officially in effect until 8 p.m. Thursday for inland Los Angeles County, the valleys, mountains, and inland Orange County. 

Temperatures in these zones are peaking between 100 and 110 degrees on Wednesday, marked by the NWS as the warmest day of the event. Coastal areas are under a less severe heat advisory, though temperatures there are still reaching the 80s and 90s.

In the Inland Empire, highs will range between 90 and 108 degrees, with low deserts reaching up to 113 degrees. Mountains below 6,000 feet are projected to reach up to 99 degrees, according to the NWS. 

Compounding the risk, a Red Flag Warning denotes critical fire danger along the 5 Freeway corridor in LA County due to a combination of high heat, low relative humidity, and powerful northwest-to-north winds. 

Overnight low temperatures will remain in the 70s, offering minimal relief for the body to cool down naturally.

Timeline:

• Tuesday, 10 a.m.: The extreme heat warning officially takes effect for major portions of Los Angeles County.
• Wednesday, 10 a.m.: The extreme heat warning expands to cover inland Orange County communities.
• Wednesday, 12 p.m. (Noon): A red flag warning begins for the Golden State (5) Freeway corridor.
• Thursday, 9 a.m.: The red flag fire danger warning expires.
• Thursday, 8 p.m.: Extreme heat warnings and coastal heat advisories terminate across the region.
• Friday through Sunday: Onshore winds strengthen and cloud cover increases, initiating a slow cooling trend into the weekend.

What they're saying:

Forecasters and health administrators are emphasizing the elevated threat to human safety posed by this heat event.

"Wednesday will be the warmest day with another 3 to 6 degrees of warming on tap for the entire area," according to the NWS. "This warming will bring 100- to 110-degree heat to the valleys, lower mountain elevations and the far interior on Wednesday. The increase in onshore flow will bring some cooling on Thursday, but not enough to eliminate the heat risk."

Los Angeles County Health Officer Dr. Muntu Davis reinforced the severity of the situation, urging people to recognize that heat is an invisible but lethal threat.

"Heat causes more deaths in the U.S. annually than floods, storms, and lightning combined," Dr. Davis said in a statement.

What you can do:

Officials advise taking immediate preventative steps to safeguard yourself and your family:

• Hydrate frequently: Drink plenty of water throughout the day, even if you do not feel actively thirsty.
• Adjust your schedule: Limit strenuous outdoor activities and exercise during the peak daylight hours.
• Dress appropriately: Wear lightweight, loose-fitting, and light-colored clothing to reflect heat.
• Check your vehicle: Never leave children or pets unattended in a car for any duration.
• Monitor symptoms: Watch for signs of heat stroke, including a body temperature of 103 degrees or higher, dizziness, nausea, a rapid pulse, or hot, red skin. Call 911 immediately if these are present.
• Find cool spaces: If your home lacks air conditioning, seek refuge in public spaces like shopping malls, libraries, or designated county cooling centers. You can find nearby cooling locations, community pools, and splash pads by calling 211 or visiting the county's emergency site.

What's next:

Conditions are projected to stay above normal through at least Friday.