A child sips water from a bottle under a scorching sun on Tuesday in Los Angeles. Forecasters say temperatures could reach as high as 112 degrees in the densely populated Los Angeles suburbs in the next week as a heat dome settles in over parts of California, Nevada and Arizona.

Frederic J. Brown/AFP via Getty Images

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Frederic J. Brown/AFP via Getty Images

A child sips water from a bottle under a scorching sun on Tuesday in Los Angeles. Forecasters say temperatures could reach as high as 112 degrees in the densely populated Los Angeles suburbs in the next week as a heat dome settles in over parts of California, Nevada and Arizona.

Frederic J. Brown/AFP via Getty Images

A long, intense wave of excessive heat is hitting much of the Western United States for the next week.

The region should anticipate “a prolonged and possibly record breaking heat wave,” with little relief overnight, the National Weather Service says. Heat watches and advisories stretch from Arizona to Washington state.

“In addition, the warmth combined with very little moisture and low relative humidities, will contribute to an elevated wildfire risk across parts of the northern Great Basin and northern High Plains,” the agency said.

Across California, temperatures are expected to be more than 10 degrees above normal, warns the organization that manages the flow of much of the state’s electricity.

The California Independent System Operator expects that demand on Labor Day will reach the highest point so far this year, and that it will ask Californians to take energy conservations steps.

“During a Flex Alert, consumers are urged to reduce energy use from 4-9 p.m. when the system is most stressed because demand for electricity remains high and there is less solar energy available,” the organization said. “The top three conservation actions are to set thermostats to 78 degrees or higher, avoid using large appliances and charging electric vehicles, and turn off unnecessary lights.”

Lowering the strain on the grid will help hold off more drastic measures, the organization said, including the possibility of rotating blackouts.

Las Vegas is projected to see a week of high temperatures at or near 110 degrees, with nighttime “lows” of 85 degrees or higher. Both are more than 10 degrees above the city’s average September weather.

In response to the heat wave, the city of Los Angeles is opening nine cooling centers for extended hours, and encouraging residents to exercise caution when outside and to keep a close eye on the health of their children, pets and neighbors. Governments across the region are taking similar steps.

“Take this heat seriously, even if you’re healthy, because the predicted temperatures are nothing to take lightly,” Dr. Geoffrey Leung, the public health officer of nearby Riverside County, said in a statement. “Even remaining outdoors for short periods of time can impact your health.”

LAist has an extensive list of tips for keeping safe in hot weather, and for spotting the symptoms of heat illnesses.