California poised for another punishing, record-breaking heat wave

In a summer in which climate change has left its mark on the Northern Hemisphere, California is expected to begin another record-breaking heat wave on Wednesday, with temperatures forecast to hit 115 degrees Fahrenheit inland over Labor Day weekend.

Computer modeling conducted last week accurately predicted that a heat dome would park itself over Central and Southern California for days on end, bringing triple-digit temperatures to much of the state.

And in states like Texas, which has endured punishing stretches of extreme heat this summer, officials are warning that California's power grid could suffer outages and see Flex Alerts, in which consumers are asked to conserve energy at night as demand for electricity surges.

“If weather or grid conditions worsen, the ISO [California's Independent System Operator] may issue a series of emergency notifications to access additional resources and prepare market participants and the public for potential energy shortages and the need to conserve,” ISO officials warned in a statement released Tuesday night. “The power grid operator expects to call on Californians for voluntary energy conservation via Flex Alerts over the long weekend.”

California utility company Pacific Gas & Electric posted tips on how to “lower AC costs and still stay cool indoors during the prolonged heat” that included adjusting home thermostats to 78 degrees or higher, closing window shades in the afternoon and avoiding cooking using an oven.

As Californians have learned through repeated experience in recent years, prolonged hot weather also means an increased risk of wildfires. The current heat wave is no exception, with virtually all of the state in the midst of "severe drought," and many regions classified as experiencing “extreme” or “exceptional” drought conditions, according to the U.S. Drought Monitor.

The National Weather Service posted an “excessive heat warning” Wednesday, cautioning Northern California residents, especially those who live in inland areas, that there will be “very high risk of heat stress or illness” for the entire population, and warned people to avoid being outdoors in the sun between 10 a.m. and 6 p.m. during the hottest days.

Sacramento, the state capital, is approaching a record for the number of days with temperatures of 100 degrees Fahrenheit and higher, and is expected to hit 112 degrees on Labor Day, which would be a record high.

So far this summer, Sacramento has recorded 34 days of temperatures over 100 degrees Fahrenheit. “The most we’ve ever seen was 41 days, and that was set in 1988,” Katrina Hand, a meteorologist at the Sacramento NWS, told the Sacramento Bee. “So there’s a real good chance we’ll tie that or exceed that record for days above 100 degrees — at least for the downtown Sacramento area.”

The most extreme heat of this latest wave is likely to hit the southern part of the state, with temperatures expected to reach 115 degrees Fahrenheit in the Inland Empire and into the triple digits in the San Fernando Valley near Los Angeles.

Since the dawn of the Industrial Revolution, when mankind began pumping greenhouse gases into the atmosphere at an unprecedented rate, average summer temperatures in California have risen by roughly 3 degrees Fahrenheit, according to data from the Scripps Institution of Oceanography at the University of California, San Diego. More than half of that increase has occurred since the early 1970s, the Scripps website said.