Why this summer’s L.A. heat waves feel so miserable: Hotter nights, broiling beaches

On paper, Southern California’s summer heat has been “pretty typical,” in the words of Mike Wofford, meteorologist with the National Weather Service in Oxnard.

So why do so many people swear this summer has felt so unusually oppressive?

Experts point to several factors to explain the summer discomfort. Nighttime temperatures remain stubbornly high. And it’s been broiling along the coast, which typically offers a cooler respite from the heat.

“It’s been an extraordinarily, arguably record-breakingly, warm summer at night,” said climate scientist Daniel Swain, “but not so much in terms of the hottest daytime temperatures, which is what everybody always talks about in terms of how hot it’s been.”

Don’t expect any relief this week.

Southern California is staring down its hottest week of the year yet, with temperatures expected to rival daily records in downtown Los Angeles, Long Beach, Santa Monica and Burbank, according to the National Weather Service.

The latest heat wave continues what’s proving to be a sweltering summer globally as temperatures rise because of climate change, with last month tying 2024 as the warmest July since record-keeping began in 1850, per the National Oceanic and Atmospheric Administration.

Experts said they are not surprised the hot conditions are taking a toll.

Hotter nights can prolong the stress that heat places on the human body by depriving people of a chance to recover, increasing the risk of heat-related illness. Such conditions also put more strain on animals, plants and infrastructure.

Many parts of the U.S. are seeing overnight temperatures warming faster than daytime maximum temperatures, which appears to have become a hallmark of climate change in some regions, said Swain, an associate researcher at University of California Agriculture and Natural Resources.

Swain looked at Southern California climate data from June 23 to Aug. 23. In terms of average temperatures over that 60-day period, the picture was mixed, he said, with some areas falling in the middle of the pack compared with previous years and others notching notable heat. For instance, Torrance recorded its fourth-warmest period over this time frame, and Los Angeles International Airport its fifth-warmest, he said.

But when examining only average minimum temperatures, the map “looks way more interesting,” with more areas approaching or breaking records, Swain said. By that metric, it’s been the warmest summer on record in Torrance, and the third-warmest at LAX, he said.

“In short, it’s been extremely warm at night and only slightly warm in the daytime,” he said.

The pattern has persisted across the continental United States this summer but has been especially dramatic in coastal Southern California, Swain said.

Much of that is due to the recent record warmth of the near-shore ocean, as the water temperature essentially sets the floor for how cold it will get at night along the coast, he said.

Warmer ocean temperatures also cause more humid conditions near the coast, Swain said. The dew point, which measures the absolute humidity in the air, has been closer to 70 degrees than 60 for much of the summer, he said. “In some cases I’ve been seeing dew points above 70 — 72, 73 — that is like Miami-level humidity.”

After a gym session on Monday afternoon, Becky Sudbrink hit up the local UPS store in downtown El Segundo to send a package to a friend.

Sporting a blue workout tank top and black shorts, the four-year resident of the community said the heat doesn’t really compare to the humidity she’s experienced when she lived in Illinois.

But Sudbrink has noticed that the temperatures this summer have pushed her to use the air conditioning more than she would like.

This past week the evenings haven’t been too bad, but any warmer and “sleeping wouldn’t have been too good or restful,” she said.

Multiple factors, rather than just temperature, contribute to a person’s thermal burden, or the amount of heat their body carries, said Bharat Venkat, a medical anthropologist and director of the UCLA Heat Lab. Humidity is a critical one — since muggy air can hold less moisture, the sweat on a person’s body doesn’t evaporate as swiftly, he said.

“Sweating is the most powerful mechanism our body has at its disposal to cool us down,” he said.

Although the above-average ocean temperatures near the coast have been primarily due to a months-long marine heat wave, El Niño is now starting to exert an influence, Swain said. That means the warmer, stickier coastal conditions will probably stick around through the fall, and probably the first half of winter, he said. In fact, he expects warmer nighttime temperatures to be a signature of El Niño in the coming weeks and months.

In Long Beach, the conditions were compounded by a power outage that affected tens of thousands of customers, which started at 6:40 p.m. on Sunday and halted power for 22,066 customers, according to David Eisenhauer, spokesperson for Southern California Edison.

Around 11 p.m., Sumouni Basu was feeling the “sweltering heat” inside her apartment. Without electricity to run her ceiling fan, she decided to pack up a few things and her cat Loki and stay with a friend who was in a part of town with power — a place that would be cooler than hers.

Basu said that when the power went out earlier in the evening, she was in the shower and believed the outage could have been due to a short circuit in her older building.

She soon realized the blackout affected her building and her street.

“It was right around when the sun was setting, and I have a west-facing window, so it was just really hot,” Basu said.

Her shower not only was disrupted, but it was in vain because Basu started to sweat immediately.

“I was pretty uncomfortable,” she said.

Without electricity, Basu couldn’t access her car from the building garage, an entrance that’s powered by electricity, so she walked 15 minutes to her dinner with a friend. On the walk all along Fourth Street, she noticed families sitting on their stoops or porches and generally more people trying to beat the heat outside of their homes.

When she returned from dinner, Basu noticed Loki was a little sluggish and she worried how she and her cat would get through the night.