July’s searing temperatures made it California’s hottest month on record, according to national weather data. The average temperature statewide was 81.7°, almost two degrees warmer than the previous record set in 2021.
“That is a huge margin,” said Daniel Swain, a climate scientist with UCLA. “Not only did we break the previous record, but we essentially shattered it.”
Heat waves lasted through most of July in much of the state, with daily temperature highs soaring over the triple digits. And, crucially, temperatures stayed warm overnight, increasing the average temperature for the month.
Yet “people’s experience depending on where they lived in California was very different,” Swain said, with inland cities experiencing the worst warming.
Sacramento and Fresno each had their hottest July numbers on record at 81.1° and 90.0°, respectively. Alameda, Contra Costa and Santa Clara counties each deviated more than 7 degrees above historical averages with July average temperatures of 76.7°, 78.3° and 76.5°.
Coastal cities experienced less severe increases. San Francisco’s July averaged 66.6°, about 3 degrees above its historical mean, but still the hottest it has ever recorded.
The National Oceanic and Atmospheric Administration has recorded monthly temperatures for more than 100 years, and California has broken all-time monthly heat records three times in the past decade. A blistering July in 2018 averaged 79.6°F in California, which was knocked out by a 79.8°F average in 2021. The previous record of 79.5°F was set in 1931.
While July’s temperature spike was “remarkable,” Swain said, it wasn’t surprising.
“It is, unfortunately, very consistent with expectations that we’re going to see hotter and hotter summers,” Swain said.
California, alongside the rest of the world, is “stair-stepping upward” to a warmer climate, Swain said. Some years will be relatively warmer or cooler than others, so it’s possible next summer’s heat waves could be less severe. But on the state’s current climate trajectory toward warmer summers, a July as hot as this one will become “ordinary, if not on the cool side of things” in the near future, Swain said.
With July’s punishing heat came the most active start to fire season in more than a decade. Over 629,000 acres, nearly a thousand square miles, burned in the state through July 30.
The summer heat follows a wet winter and spring, which caused extra grass and brush to grow. Then, scorching temperatures “kiln-dried” the dense vegetation, creating a “one-two punch” for wildfires, Swain said. The lack of relief from the heat overnight also increases the risk of wildfires.
Fire season often doesn’t peak until later into the fall, Swain said. Wildfire activity “may continue to be more active than normal,” though we may see a shift in the location of the fires, Swain said.