Why Does It Get So Hot In Los Angeles?

The season of heat has finally arrived which means you may soon be sweating in front of your air conditioner and wondering: why does Los Angeles get so hot?

'Tis the season

A few factors ramp up the heat as the summer months trundle along.

As the weather starts to warm, ocean temperatures rise and the June Gloom melts away, leaving us without a consistent marine layer to deflect sunlight from our neighborhoods. The increase in solar radiation, which also comes with the longer days, heats things up.

Around this time of year, high pressure systems start to set up over the region as well, acting like domes, both trapping in heat and blocking cool air from flowing over us and providing relief. They’re responsible for the more extreme heat waves we experience.

The San Fernando Valley is basically a giant bowl that traps heat.

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Jacob Margolis

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LAist

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Geographical conditions also play a major role, especially in places like Woodland Hills in the San Fernando Valley, which is regularly one of the hottest spots in the city.

While people along the coast benefit from both the marine layer and cool ocean air, the Santa Monica Mountains can prevent the coastal breeze from moving inland. Meaning, the hot air gets trapped in the gigantic bowl that is the Valley and just sits there.

Concrete, asphalt and black-tiled roofs also absorb heat and radiate it back out into the atmosphere in what’s known as the urban heat island effect.

Compared to rural areas, temperatures can be as much as six degrees higher during the day and 22 degrees hotter at night, making it harder for us to cool off. This impact is often more pronounced in low-income communities and communities of color for a variety of reasons such as having less tree cover to cool things down.

Then comes fire weather

After we’ve been cooking for several months under high pressure conditions and all our fuels are nice and crispy, the blustery Santa Ana winds flow in from over the Great Basin.

They pick up speed, dry out and heat up as they charge right at the West Coast, driving up temperatures and fueling catastrophic fires.

You can see how the Santa Ana winds blow in this satellite image, where they're pushing plumes of smoke out towards the ocean in October 2007.

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NASA/Getty Images

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Getty Images North America

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The winds usually peak in December, which isn’t a problem if the rainy season arrives on time but we’ve seen strong high pressure ridges set up off the West Coast and prevent cold and wet storms from reaching us in recent years. When this happens, dry and hot conditions can extend into winter.

The future of heat in LA

The intensity and length of heat waves is likely to increase as the climate continues to change, with some of the hotter parts of LA possibly seeing 30 or so additional days with temperatures above 90 degrees by 2050, according to the Los Angeles County Climate Vulnerability Assessment.

The coastal clouds that contribute to cooling also seem to be decreasing in frequency, raising concerns about what this’ll mean for communities that they help keep cool, especially given that a whole lot of people here don’t have air conditioning.

When it is quite hot, you should consider postponing outdoor activities because heat can be deadly, even for those that you might not expect. To that end, there are countless workers who have to choose between working in deadly conditions or potentially losing out on a paycheck partly because of a lack of adequate worker heat protections in California.