The heat can even lead to death. But experts say we likely undercount heat-related fatalities, underestimating the true toll of extreme weather.
"Heat waves don't get the respect they deserve," says Dr. David Eisenman, a professor at UCLA. "They are the most common natural disaster."
For example, Eisenman says, an elderly person may come into his clinic feeling nauseous and dizzy. They get diagnosed with dehydration and kidney failure and later die. But the root cause isn't fully investigated and linked to the weather.
"No one goes to their home to see that it was 85 degrees in their home, no one gets the history that they were living there and no one was checking in on them, they weren't drinking (water)," Eisenman said.
"And if no one gets that history, it's recorded that this person died from, say, kidney failure, but it's not recorded that all of that was induced by the heat and dehydration in their hot house."
The numbers of official heat deaths in Southern California may sound surprisingly low at times.
Riverside County has recorded 24 deaths so far this year, with 12 in San Bernardino County and none in Orange or Ventura counties.
Los Angeles County, which has a much bigger population than any of the other counties, has only recorded two heat deaths.
Officials say it can take up to three months for the data to be finalized. But Eisenman says even so it's likely heat-related deaths are undercounted.
"LA County has many millions more people than the Inland Empire, and even though it's not as hot here, we would expect to have more than just two per year."
But you can at least track ER visits by ZIP code if you draw on heat maps produced by UCLA.
One of the biggest trouble spots is South Los Angeles. It might not be as hot as the Inland Empire, but there are more homes that lack air conditioning, he notes.
For example, Leimert Park gets more than double the number of hospital visits than neighboring Culver City.
"Those are areas that were historically redlined, and in those areas - Inglewood, Compton, the ports - we see very high rates of heat-related injuries, much higher than neighboring towns."
And it's not just the triple digits outdoors that pose a danger. Eisenman says it only needs to get up to about 85 degrees inside your home or apartment. If you're subjected to those temperatures for more than a day or two without staying hydrated it can be extremely dangerous.
"The bottom line is people need access to cool air, in order to be protected from extreme heat."