PHOENIX (AP) — Parts of California, Nevada and Arizona are expected to bake this week as the first heat wave of the season arrives with triple-digit temperatures forecast for areas including Phoenix, which last summer saw a record 31 straight days of at least 110 degrees Fahrenheit (43.3 Celsius).

By Wednesday, most of an area stretching from southeast California to central Arizona will see “easily their hottest” weather since last September, and record daily highs will be in jeopardy from Las Vegas to Phoenix, the National Weather Service said late Monday.

Excessive heat warnings have been issued from 10 a.m. Wednesday to 8 p.m. Friday due to the “dangerously hot conditions,” the weather service said.

Fire crews will be on high alert especially in Arizona, where fire restrictions went into effect before Memorial Day in some areas and will be ordered by Thursday across most of the western and south-central parts of the state, authorities said.

Fire forecasters at the Southwest Coordination Center in Albuquerque, New Mexico, said weather in the region doesn’t typically become so hot until mid- or late June.

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“It does seem like Mother Nature is turning up the heat on us a little sooner than usual,” Tiffany Davila, spokesperson for the Arizona Department of Forestry and Fire Management, said Monday evening.

“We can’t back down from a fire just because it’s pushing 113 degrees outside. But we do keep a close eye on everybody in the field. Make sure they are keeping hydrated and taking more breaks than they normally would,” she told The Associated Press.

Highs on Monday reached 110 F (43.3 C) at Death Valley National Park in California near the Nevada line, 103 F (39.4 C) in Phoenix and 105 F (40.5 C) in Needles, California.

Slightly above normal temperatures are forecast for the region on Tuesday before they start heating up on Wednesday.

In Las Vegas, where the high topped out at 103 F (39.4 C) on Monday, temperatures will soar to 10 - 15 degrees above normal during the second half of the week — peaking at 111 (43.8 C) on Thursday.

A high of 120 F (48.8) is forecast for Thursday at Furnace Creek in Death Valley.

The current forecasted high of 113 F (45 C) for Phoenix on Thursday would break the daily record high of 111 F (43.8 C) set in 2016. Last summer, the high there reached 110 F (43.3 C) or higher from the last day of June through the entire month of July. At least 400 of the 645 heat-related deaths that occurred last year were during that monthlong period.

Phoenix, Maricopa County and Arizona state officials this year are striving to better protect people from ever higher temperatures. Those most in danger from the heat are people outdoors, especially homeless people in downtown areas who often don’t have access to sufficient shade, air conditioning and cold water.

Governments this year are setting aside more money so some cooling stations can stay open longer and on the weekends, including two that will keep their doors open overnight.

Mesa, Arizona, Mayor John Giles said they are “committed to ensuring that those most vulnerable to heat exposure have access to essential life-saving services, including hydration and cooling stations and daytime respite centers.”

Additional fire restrictions set to go into effect Thursday across Bureau of Land Management lands in Arizona will come with bans on campfires, open flames and recreational shooting in some areas, BLM spokesperson Delores Garcia said.

“As the heat goes up, so does the threat of wildfires,” she said.

“We have noticed the effects of the winter and early spring rains really brought up the vegetation and the higher heat has just cured that vegetation. That’s what we are seeing as the driving factor. And then winds on top of that,” Garcia said.

Meanwhile, California’s largest wildfire so far this year was significantly surrounded on Monday after blackening a swath of hilly grasslands between San Francisco Bay and the Central Valley.

The California Department of Forestry and Fire Protection said the Corral Fire was 75% contained after scorching more than 22 square miles (57 square kilometers).

One home was destroyed and two firefighters were injured. The wind-driven fire erupted Saturday afternoon and at one point thousands of people were under evacuation orders.

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Sonner reported from Reno, Nevada.