A Southwest heat wave is on the way, the weather service warns

More than 25 million people are under heat alerts, and more than 50 daily high-temperature records could be broken through the weekend — including in Death Valley, California, one of the hottest places on earth.

“Don’t underestimate the heat! Heat is one of the most deadly weather hazards, so be sure to practice heat safety this week,” the Sacramento National Weather Service tweeted.

“Record high temperatures will be [felt] across portions of Texas on Wednesday and Thursday and expanding into California on Friday,” the Weather Prediction Center said Wednesday morning.

High pressure will create a heat dome over the Western US. The dome will trap any escaping radiation and send it back to the ground, while the sun’s rays continue to penetrate through.

This, combined with arid soils from an extensive and long-term drought, will allow temperatures to rise to record levels over parts of California and the Southwest, with high temperatures from the upper-nineties to over 110 degrees on Friday, the Weather Prediction Center said.

Here is when and where the heat will be the worst.

Texas-size heat leaves the state sizzling

“Hot again” is how the San Angelo National Weather Service started their forecast discussion this morning, as the mercury will rise in West Central Texas on Wednesday and Thursday afternoons.

High temperatures will break the century mark this afternoon and highs will intensify as the week progresses. Peak intensity is likely from Saturday through Monday, the San Angelo weather office said.

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Major cities in Texas will see high temperatures over 100 degrees. Austin, San Antonio, Dallas, and Houston will likely hit the figure once, twice, maybe even three or more times before the week is over.

Above-average temperatures this weekend are likely to put the Texas power grid to the test.

During the state’s heat wave last month, Texans were encouraged to conserve power by raising thermostats to 78 degrees and refraining from using major appliances during peak hours.

First heatwave of the year for Las Vegas and Phoenix

As this weather pattern remains over Texas into and through the weekend, it will expand into Southern California as well as Nevada and Arizona Thursday into Friday.

The first excessive heat event — level 4 of 4 on the weather services experimental heat danger scale — of the season is now upon us, the weather service’s Phoenix office said.

“The first heatwave of the year has numerous climate sites threatening daily record highs and record warm lows,” added the Las Vegas National Weather Service.

Death Valley is forecast to reach 121 on Friday. If it does, that will break the daily record of 120 set back in 1994.

Las Vegas will also flirt with daily records, with temperatures close to 109 both Friday and Saturday.

See how hot the temperature will climb where you live

“High temperatures will approach 110 degrees already this afternoon and are expected to top out between 110 and 115 degrees across the lower deserts by Friday and last through the weekend,” the Phoenix National Weather Service said.

Nighttime low temperatures will be near a record high as well.

Las Vegas is only forecast to drop to 84 degrees Saturday morning, for example. The previous hot low temperature was 81 in 1996.

What makes this so dangerous is when temperatures remain this hot overnight, your body doesn’t get a break from the extremes.

The heat should lessen early next week, the Phoenix National Weather Service said, with temperatures falling back to near-normal readings.

Both the Las Vegas and Phoenix weather offices also say Sunday might not be as hot as initially thought.

Interior California will see ‘high’ heat risk

Similarly in California, the worst will be Friday.

If you are on the California coast, you will escape the heat. The state’s interior won’t be so lucky.

“Warming and drying trend with triple-digit heat by late-week for the Central Valley,” the Sacramento National Weather Service said. “The hottest day will be Friday, with little overnight relief from the heat.”

The heat risk will be high — level 3 of 4 — on Friday for most of interior California.

“Daytime temperatures could reach at least 100-105° across the Valley on Friday, which combined with warm overnight temperatures will produce high risk for heat impacts for the general public,” the Sacramento weather office tweeted.

All of the weather service offices had similar heat safety messages with tips for staying safe during excessive heat events: Try and avoid caffeine and alcohol, which can dehydrate the body. Instead, drink plenty of water and try to find air conditioning.

The drought is making this heat worse

An ongoing drought continues to plague the Southwest. And one of the many drawbacks of drought — and dry soil — is its impact on temperatures.

When there is no moisture in the soil or in plants, there is no evaporation or evapotranspiration, both of which are cooling processes that add moisture into the air and stabilize the air temperature.

“Basically, the drier the air, the easier it is to get to a high temperature,” Bryan Jackson of the Weather Prediction Center told CNN Weather. “When there’s more humidity, the temperature can be suppressed.”

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