Los Angeles, US West Brace for Second Bout of Record March Heat

Los Angeles and the U.S. Southwest are set for a second record heat wave in two weeks as temperatures soar, potentially straining electric grids, melting snowpack and raising health risks.

Tuesday’s high in downtown Los Angeles is forecast to reach 97F (36C), possibly climbing to 98F by Thursday, according to the National Weather Service. Commercial forecaster AccuWeather Inc. said temperatures may rise as high as 99F, which would tie March 29, 1879, for the warmest March reading on record.

Heat advisories and excessive heat warnings span parts of Nevada, Arizona and California, extending to San Francisco, with temperatures forecast to be 15F to 30F above normal.

“The L.A. area really starts to fire up today,” said Tyler Roys, a meteorologist with AccuWeather. “Basically, it is record-breaking heat for many places.”

Through next Monday, 450 daily high-temperature records may be broken or threatened across the US, most in the West, the US Weather Prediction Center said. An additional 334 record warm overnight lows also may be set or tied.

The early heat will drive up energy demand as residents and businesses turn to air conditioning. It will also dry out vegetation, raising wildfire risk.

A bigger concern is faster snowmelt in the mountains, which would reduce this year’s water supplies for California and other western states. Unlike the eastern US, which typically receives regular rainfall, much of the West relies on winter storms and mountain snowpack as a natural reservoir that stores water through the winter and releases it gradually in the spring and summer.

“What we have to be worried about is this heat dome is going to start the melting process of the snow in the higher terrain,” Roys said, meaning that what the state needs in the summer “won’t be there.”

California had its second-warmest winter on record, according to the US National Centers for Environmental Information. All-time high temperatures in nine states have left the region with below-normal snowpack. As of March 12, Colorado had its lowest on record, the National Integrated Drought Information System said.

For California, the worst of the heat will last through Friday, said Brian Hurley, a senior branch forecaster at the US Weather Prediction Center. While such temperatures are typical in July, they are unusual for March and will force Californians and residents in other parts of the West to act as if summer has arrived.

“The biggest thing is it’s going to be unseasonably warm early,” Hurley said. “That is really the main story.”