Across Los Angeles, at festivals, botanical gardens and even the beach, the heat is the hottest topic. Residents lament astronomical electricity bills or lack of air conditioning. Memes about the swelter multiply. Neck fans abound.
Weather is often the easiest small talk in a region whose normal summers offer pleasing aridity and cool nights. But this year, there’s a disquieting debate: Is humidity making things worse?
Meteorologists don’t track humidity as closely as temperature, but trends point to stickier air than usual in Southern California, from San Diego to Santa Barbara. That’s in part because the rapidly warming Pacific Ocean off the coast feels like a bath tub.
The region’s weather is generally so pleasant that residents are keenly attuned to any disturbance.
“I grew up in Virginia, which is way more humid than here, and I actually do think it has felt a little more humid this summer,” said Lindsay Lazarus, 41, who sat on a picnic blanket as her son darted around a park’s splash pad near the Los Angeles River.
Her friend, Sarah Rockwood, 37, was less sure: “It’s not even humidity to me — like the sun is just right here all the time,” she said, gesturing above her head. “But I don’t know.”
Temperatures, while high, are not eye-popping by the standards of, say, Arizona. And yet, something has felt different for residents accustomed to waving off the forecast with assurances that it’s “a dry heat.”
Dew points — the measure of water vapor in the air — have nudged slightly higher than average much of the summer. The higher the dew point, the more humid it feels, the frizzier the hair, the more stubborn the sweat stain.
The human body experiences heat more intensely, fighting to cool itself as the natural air conditioning of perspiration becomes less efficient.
“This is why humid heat waves are so oppressive compared to dry heat waves,” said Alexander Gershunov, a research meteorologist at the Scripps Institution of Oceanography at the University of California, San Diego.
Sapphire Ventura, 34, was dragging.
“It feels pretty unbearable,” she said, as she offered her daughter a towel at the splash pad. “I did not grow up with this weather.”
She said she could tell there was more moisture in the air, thanks to little indicators: She was getting sweatier faster, her hair puffed up, her dog started panting earlier in the day.
“As moms, you have that greater attention to detail,” she said. “It’s like, ‘Whoa.’”
For others, one major change has been mosquitoes, which thrive in more humid climates but have historically been less omnipresent in Southern California. This summer, friends have been warning one another in dire tones to break out the DEET. For good reason: West Nile virus activity across the state is at a five-year high.
Two factors are driving up dew points, according to Ryan Kittell, a meteorologist with the National Weather Service office in Oxnard, Calif.
Winds high in the atmosphere are pulling moist tropical air from Mexico into Southern California. And the Pacific Ocean off the coast has been five to 10 degrees above normal. Warmer water evaporates faster.
“It puts a tremendous amount of moisture in the air, which gets pushed inland with the sea breeze,” Mr. Kittell said.
The marine heat wave that started in February is expected to be exacerbated by the El Niño weather pattern, and “cause it to persist into fall and winter, and even into next spring,” said Art Miller, a research oceanographer emeritus at the Scripps Institution of Oceanography at the University of California, San Diego.
In coming days, much of the region is expected to record the summer’s hottest temperatures, while moisture from a tropical storm simultaneously flows north. Clouds on Thursday and Friday could cut the heat but will also drive up humidity.
“It’s going to be quite uncomfortable,” Carol Ciliberti, a Weather Service meteorologist.
Los Angeles officials said that not only will the heat be uncomfortable, it will be dangerous, and have issued an extreme weather advisory in effect until Friday. Mayor Karen Bass said that hundreds of facilities, including libraries and recreation centers, will be open for residents looking to cool off.
Dr. Nichole Quick, an official with the Los Angeles County Department of Public Health, said that higher nighttime temperatures complicate getting relief while asleep — a crucial respite, especially as heat waves become more frequent and longer as a result of climate change.
All that, she said, has contributed to spikes in heat-related illnesses and deaths.
Still, the heat didn’t scare off tourists at the region’s top destinations. At the Griffith Observatory, an overlook made famous by countless onscreen appearances, visitors carried umbrellas as they sweated and puffed up the hill from the parking lot.
Few locals were out, but Marie Solano, a 17-year-old tourist, who wore a pink printed dress and impeccable makeup, said she felt fine.
“It’s manageable,” she said with a smile.
Her mother, Cynthia Ulloa, 41, shaded her head with her jacket but said that the weather felt “similar to our country.”
They were visiting from Costa Rica.
