California Braces for Dangerous Weekend of Record-Setting Heat

U.S.|California Braces for Dangerous Weekend of Record-Setting Heat

California is bracing for another dangerous heat wave and record-breaking temperatures this weekend, just two weeks after a heat dome descended on the normally temperate Pacific Northwest, killing hundreds of people and capping North America’s hottest June on record.

The National Weather Service issued an excessive heat warning for much of California beginning Friday at noon and extending into Monday night. Forecasters are predicting dangerous triple-digit highs and warm overnight lows for much of the state’s inland regions.

According to Sarah Rogowski, a National Weather Service forecaster, California may experience record-breaking highs in the central part of the state on Friday, over the weekend and into Monday, with highs 10 to 15 degrees higher than average in some parts of the state.

On Friday, the Central Valley can expect temperatures up to 113 degrees Fahrenheit, Ms. Rogowski said. Southern California’s inland regions could reach 117 degrees.

The hottest weather is forecast for the weekend. The Sacramento Valley is projected to reach a record-breaking 115 degrees on Saturday and Sunday. Temperatures will run even higher in Death Valley, which may hit 123 on Saturday. Coastal regions will still be very hot, but spared from the extreme heat by marine air. Very minor relief from the heat could come on Monday; the Central Valley will still be dealing with temperatures up to 110 degrees.

“This is on top of the heat wave we saw earlier in the summer,” Ms. Rogowski said. “It’s been a pretty hot period with not much relief across the state.”

As in the recent Pacific Northwest heat wave, prolonged heat during the day paired with warm nights can lead to a cumulative heat effect, which has forecasters worried about an increase in heat-related illnesses.

“People don’t have that recovery time,” Ms. Rogowski said. “You don’t have time to cool off your home and to really just recover from the heat.” Lows in some regions will be in the high 80s — the usual high for the state during the late summer months.

The back-to-back heat surges that California has experienced since the beginning of summer are coming a lot earlier than usual, according to Brian Ferguson, deputy director of crisis communications for the California Office of Emergency Services.

“We believe that California is very clearly experiencing the impacts of a changing environment,” he said. “We’re seeing drought conditions we haven’t seen before, and there is a cascading impact, but it really all comes back to climate.”

While tying a single heat wave to climate change requires extensive attribution analysis, scientists in Europe found that the recent extreme heat in the West Coast would almost certainly not have happened without it, because the jump in temperatures was so erratic. And in general, it is settled fact that heat waves around the world are lasting longer and growing more frequent and more dangerous.

The 2018 National Climate Assessment, a major scientific report by 13 federal agencies, noted that the number of hot days was increasing and that the frequency of heat waves in the United States had jumped from an average of two per year in the 1960s to six per year by the 2010s. Also, the season for heat waves had stretched to 45 days longer than it was in the 1960s, according to the report.

It is all part of an overall warming trend: The seven warmest years in the history of accurate worldwide record-keeping have been the last seven years, and 19 of the 20 warmest years have occurred since 2000. Last year tied with 2016 as the hottest year on record, according to one analysis.

Mr. Ferguson said his office was preparing for what it calls an “asymmetrical event.” He said this weekend could present simultaneous competing challenges, with the state facing extreme heat, fire warnings and the possibility of electricity shortages all happening at once.

In preparation for the heat wave, the Office of Emergency Services said it was helping local officials with cooling centers across the state to assist those without access to air-conditioning. It was also pre-emptively positioning firefighters and fire trucks in parts of the state that have higher risks for bush fires and wildfires. A fire weather watch was in place for Northern California on Thursday afternoon.

The Office of Emergency Services is also working closely with the California Independent System Operator, which runs the state’s energy grid, to ensure that power continues uninterrupted over the weekend. Mr. Ferguson said no shortages were anticipated over the weekend, in part because of additional electricity capacity the state invested in last year, but that shortages were always a risk. He urged Californians to be mindful of alerts about electrical surges and to be ready to minimize use of appliances if needed.

“We’re competing with Mother Nature,” he said. “We’re throwing everything we have at this challenge to help keep those who are vulnerable safe.”