‘A Delight-Mare’ — Bay Area Sizzles, March Heat Wave Could Shatter Records

The Bay Area is already baking under an early spring heat wave, as unseasonably hot temperatures throughout the region climb toward all-time March records — and climate change is part of the issue.

Forecasters at the National Weather Service said that San José, Santa Rosa, Redwood City, Livermore and Salinas might set all-time high temperature records — for any day ever in March over the next week. While daily high-temperature records could be threatened in San Francisco, San José, Oakland and Napa.

“We expect a slew of daily records to be broken, and several monthly records are likely to go down as well,” wrote NWS Bay Area meteorologist Dylan Flynn in the local office’s daily forecast discussion.

Scientists point out that human-caused climate change makes high temperatures more likely, and that in the coming days, Bay Area residents shouldn’t be surprised if the heat wave sets new records.

Cities across the region are skewing 20 to 30 degrees warmer than normal, said Rachel Kennedy, a meteorologist with the weather service’s Bay Area office.

“These temperatures are usually what we would see in late July and August,” Kennedy said. “It’s almost like skipping spring and moving to summer.”

The Bay Area’s warm weather is caused by a ridge of high pressure from the subtropics building northward over the Pacific Ocean, creating a heat dome, or unusually warm conditions inland. By early next week, the ridge will sit right over Northern California.

Kennedy said that the heat wave will likely last through next Friday. She said that temperatures will remain in record territory until at least Thursday, and “Friday might be in record territory too.”

Back in 1996, Santa Rosa set a high-temperature record of 87 degrees for March.

Livermore did the same back in 1972. Tuesday’s forecast has both cities reaching nearly 90 degrees. San Francisco, Napa, and Oakland could also break their temperature records set back in 2004 early next week.

Forecasters said San José is most likely to set a new all-time March heat record, with temperatures forecasted to hit 92 degrees on Tuesday. The city could also break a record for the hottest back-to-back days for March, set on Sunday in 2004 and Monday and Tuesday in 1914.

“There’s a pretty high confidence, actually, that we are going to end up challenging or breaking those records Monday or Tuesday,” Kennedy said. “Part of the reason why these records are on the lower side is that we don’t typically see temperatures this warm in March.”

Kennedy said San José is “the city to watch” for a new all-time March heat record. Tuesday’s forecasted temperature of 92 degrees would mark the hottest day ever recorded in March for the South Bay city.

The Bay Area experienced “a comparable heat wave” between March 24 and 26 last year, Kennedy said, with Bay Area temperatures in the 80s, and across the interior East Bay and Central Coast, temperatures hitting the 90s.

Many of the current highest records date back to 2004, she said, which saw a semi-comparable, early to mid-March heat wave with temperatures in the mid to upper 80s.

“The 2004 heat wave was not as hot as this current heat wave looks,” Kennedy said. “But it set a number of records that we are challenging this week.”

Noah Diffenbaugh, a climate scientist and professor at Stanford University, said that in this current heat wave, it will take meticulous investigation to truly know the role of human-caused climate change.

What scientists do know, however, is that global warming increases the frequency and intensity of heat waves.

Diffenbaugh said that this next week’s temperatures offer “the clearest scientific evidence that global warming is playing a role.” He added that this early-season heat wave shouldn’t come as “a surprise” because climate scientists have long predicted the intensification of extreme weather events.

“We’re more likely to have really intense temperatures because global warming is acting on top of that baseline of Earth’s natural processes,” Diffenbaugh said. “This is the kind of event we should be expecting.”

Scientists at the nonprofit research group Climate Central created a Climate Shift Index that estimates the extent to which anthropogenic warming affects temperatures on any given day. The group compares the world today with a world without carbon pollution from human activity.

By comparing the two, according to Climate Central’s vice president for science, Kristina Dahl, “we can get these estimates of the fingerprint that climate change has on heat waves.”

Dahl said that due to global warming, the excessive heat across the Bay Area is two to three times more likely.

She called these days a “delight-mare.” Dahl added that although people might enjoy unusually warm weather, “there’s something really dark that’s driving these high temperatures, and that’s climate change.

“It’s hard for me to go out there and just fully enjoy the warm weather,” Dahl continued. “I look at our data and know that these kinds of temperatures really shouldn’t be happening at this time of year.”