PHOENIX (AP) — The Latest on the heat wave across the Southwest U.S. (all times local):

10 a.m.

The National Weather Service says a high temperature of 124 degrees (51 Celsius) is forecast for California’s Death Valley and that the temperature could hit 126 (52.22 Celsius) p.m. Thursday.

The temperatures are the highest forecast amid a heat wave that stretched across the U.S. Southwest on Tuesday.

Much of Arizona and parts of California and Utah are under an excessive heat watch in a week forecasters say could be the year’s hottest.

Phoenix is among the hottest urban areas in the Southwest, with highs that hit 100 (38 Celsius) by midmorning and expected to reach 114 (45.5 Celsius) in the afternoon.

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2 a.m.

California’s power grid operators are calling for voluntary electricity conservation as parts of the U.S. Southwest brace for another day of scorching heat.

With temperatures expected to top 100 degrees throughout the region, the California Independent System Operator Corp. is asking for people to ease off blasting the air conditioning or using the washer or other appliances during evening hours, when power usage peaks.

Cal-ISO says that reduces the risk of rotating power outages.

Highs in parts of the Southwest approached 120 degrees on Monday. The National Weather Service is predicting temperatures of about 117 degrees Tuesday in Phoenix, Arizona; 108 in Texas along the border and 109 in parts of Utah.

Triple-digit temperatures are expected into Thursday.