Summers are likely to keep getting hotter in San Mateo County and state

Temperatures this week ran around 5-10 degrees above normal and into the 80s, National Weather Service meteorologist Carolina Walbrun said, with areas in the Santa Cruz Mountains reaching the 90s.

Things are cooling down temporarily, according to another National Weather Service meteorologist, Brayden Murdock, who said Saturday should be the coolest day of the week with Bayside temperatures in the mid-60s and inland cities at a balmy mid-70.

But the warmest 10 years on record have all occurred in the last 15 years, Climate Prediction Center meteorologist Cory Baggett said, and Northern California isn’t exempt.

The Pacific Ocean keeps temperatures more moderate in California’s coastal-adjacent regions in comparison to Central Valley counterparts — where heat was reaching over 110 in some cities earlier in the month — but climate change is making for more extreme weather across the state, country and world.

“There’s certainly the human cause factor. Greenhouse gasses collect the heat … and reflects it right back downward, reemits it downward, and just keeps that heat trapped on the surface of the Earth,” he said. “I think the West, unfortunately, is one of those areas where some of this heat is concentrated. It’s almost like an amplification of the natural pattern.”

Summer weather patterns are simpler to classify into trends, particularly in the West, where heat is slowly and steadily increasing year by year, Baggett said. Winter weather can be more variable.

The previous winter was classified by an El Niño weather pattern, marked by warmer temperatures in the tropical, equatorial Pacific that pushes the Pacific jet stream south — impacting storm tracks and making it easier to predict cooler temperatures and increased flooding along the California coast.

La Niña is an opposite weather pattern — one we’re likely to see this year — defined by colder temperatures in the equatorial Pacific that historically brings drier winters with less precipitation, particularly to California’s southern half.

But climate predictions for the upcoming winter, particularly in the northern half of California, are staying at equal odds for hotter or colder climates, Baggett said. 2022, a La Niña year, was one of California’s wettest winters on record, making climate scientists wary of using it as a predictive tool.

“Our confidence gets shaken a little bit when we have, say, a strong El Niño, La Niña, and it doesn’t work out like history has shown it should work out,” he said. “Our confidence takes a hit when that happens. So that’s why you kind of see a lot of equal chances on the map right now.”

Winter might still be up in the air, but residents should plan for hot summers for the foreseeable future — and make advance plans to be in air-conditioned spaces during extreme heat, drink plenty of water and avoid overexertion.

“The long-term trend is not in favor of anything cooling off any time soon,” Baggett said.