The Latest: California urges people to conserve energy

PHOENIX – The Latest on excessive heat in the U.S. Southwest (all times local):

1 p.m.

The operator of California's electrical grid is calling for voluntary conservation of power due to high temperatures in most of the West, reduced electricity, tight natural gas supplies in the Southern California area and high wildfire risk.

The California Independent System Operator says a so-called Flex-Alert will go into effect statewide from 5 p.m. to 9 p.m. Tuesday and Wednesday.

The measure is aimed at conserving power in the hours when air conditioners are typically at peak use.

The National Weather Service issued an excessive-heat warning Monday morning for almost all of Southern California through Thursday.

Heat advisories will go into effect Tuesday up the Central Coast and through the Central Valley into Oregon.

Excessive heat warnings are also in effect in southern Arizona, California's southeastern desert and parts of Utah and New Mexico with highs in some areas forecast to reach nearly 120 degrees on what could prove to be the hottest days of the year.

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11 a.m.

An excessive heat warning was issued for a broad swath of the southwestern U.S. Monday with temperatures expected to approach 120 degrees (almost 49 Celsius) this week in what forecasters say could prove to be the hottest days of the year.

The National Weather Service says southern Arizona will experience temperatures from 112 to 119 degrees (44 to 48 Celsius) through Wednesday.

The heat warning extended to southeastern California, including desert communities such as El Centro, Palm Springs, Twentynine Palms and Blythe, as well as north to Las Vegas and other parts of Nevada.

Parts of Utah were also issued an excessive heat warning with temperatures this week expected to approach 109 degrees (43 Celsius).

The weather service said the warning for Utah's Dixie and Lake Powell regions will be in effect Tuesday through Thursday.