Dangerous heat wave hits LA: How long will it last? How high will temperatures rise?

The National Weather Service has issued an extreme heat warning for Southern California, warning that as temperatures rise over the next few days, the state’s most vulnerable residents could be at risk.

A timeline

Compared to Monday, Tuesday’s temperatures in much of the Los Angeles Basin should rise to 3 to 6 degrees, and up to 8 to 10 degrees in the Antelope Valley, according to the weather service’s morning forecast.

Temperatures in the region could range from 90 to 110 in the hottest parts of the country, the weather service said.

An extreme heat warning extends across the mountains between Santa Barbara and Los Angeles counties and the inland deserts.

“Moist conditions will add to the heat and the effects of the heat may be severe,” the agency’s extreme heat warning said. “Heat effects will increase throughout the week, with warm low temperatures at night providing little relief from the heat.”

Highs on Wednesday, far from the coast, will range from 90 to 105 degrees across much of the region, health officials warned.

An extreme heat warning is expected to last until Thursday evening before temperatures begin to drop on Friday.

He felt the heat

In Los Angeles County, the San Fernando Valley will likely see the highest temperatures, with the Woodland Hills expected to reach 110 degrees Wednesday.

The Antelope Valley could also reach 110 degrees, while Santa Clarita will be behind at 105 or 106 degrees, forecasters said.

Low temperatures across the region will likely stay in the 70s even overnight, providing little relief and increasing health concerns.

Fire hazard

Despite widespread thunderstorms, the heat brings more fire hazards. Several wildfires have broken out in the state in the past week, including a new one in Los Angeles County on Monday.

The Zebra Fire started around 7 a.m. Monday near State Route 39 and Mountain Laurel Way in Azusa and has closed the Sierra Madre Highway. It was 25 acres on Monday night.

Heat health tips

Here are some basic tips from the city of Los Angeles:

• Drink plenty of cool water; always have water.
• Wear loose, light-colored clothing that will keep you cool. Wear sunscreen and a hat to protect yourself.
• Check on neighbors who may be at risk of heatstroke, especially those without air conditioning.
• Never leave children or pets in the car – not even for a minute. Temperatures inside a car can quickly rise to deadly levels.
• When working or playing outside, take frequent breaks to drink water and cool off in the shade.
• Keep pets indoors if possible. If they are kept outside, give them plenty of water and shade to rest.
• Symptoms of heat-related illness include dizziness, fatigue, fainting, headache, muscle cramps and increased thirst. If you experience these symptoms, seek medical attention.

Public health officials say heat-related illnesses, such as heat exhaustion, are more common during extreme heat.

Common symptoms of heat-related illness include vomiting, dizziness, confusion, and hot, red, dry, or moist skin.

The first sign of heat-related illness that can lead to heat exhaustion or stroke is heat cramps, according to the National Weather Service. Burning cramps are painful muscle cramps and spasms that often occur in the legs and abdomen followed by profuse sweating.

If you or someone else is suffering from heatstroke, apply firm pressure to tight muscles or rub gently to relieve the spasm. Drink water unless you feel nauseous, then stop. If the cramps last more than an hour, seek medical attention immediately.

If you see or experience any symptoms of heat-related illness, move to a cool place and call 911.

Check out the people at risk of heat-related illness by checking out:

• cool face
• excessive sweating
• difficulty walking around
• common symptoms of heat-related illness

If you see them showing any of these signs, get them water and help them move to a cool place.

Times staff writers Karen Garcia and Grace Toohey contributed to this report.