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A view of mountains on the coast with a backdrop of the sunset among the clouds.
Scenic view of sea against sky during sunset in Half Moon Bay, San Mateo County. (Eric Thurber/500px/Getty Images)

Fall in the Bay Can Get Toasty. Here's Where You Can Still Find Crisp, Chilly Temperatures

Fall in the Bay Can Get Toasty. Here's Where You Can Still Find Crisp, Chilly Temperatures

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Summer might be over for most parts of the U.S., with the heat slowly dissipating and cooler temperatures taking over, making way for the new season.

But for many of us in the San Francisco Bay Area, warmer days are just beginning. And as the fall equinox arrives, you might find yourself still longing for that sense of autumn that brisk, cool temperatures can bring — or just the kind of fall vibes that you’re seeing others enjoying in places like the East Coast on Instagram.

Fortunately for us in the Bay Area, not only can you find gorgeous fall foliage and cider-serving apple farms all around Northern California, but access to trails with picturesque views — suitable for warm or cool temperatures — is also readily available for your autumnal enjoyment.

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Read on to learn more about why San Francisco’s fall can sometimes feel like summer, and find recommendations for parks and trails you can explore to escape the heat. (And for when it does eventually get chillier around the Bay Area, we’ve got a few ideas on where you can find warmer temperatures, too.)

Fall: When San Francisco really warms up

Fogust. No-sky July. June Gloom. May Gray.

Whatever pet name you may have for San Francisco’s highly variable conditions, this city’s temperatures are so unique due to there being so many microclimates. The proximity to the Pacific Ocean, different terrains and the effects of urban heat islands are just some of the reasons for that.

In San Francisco, September and October are the most pleasant, warm, and generally fog-free months. That’s also when it’s most common for San Francisco to experience heat waves, which on rare occasions can push north of 100 degrees.

In fact, the hottest time of the year for San Francisco is actually not until after the autumn equinox.  The average warmest day of the year for our dear foggy city is September 24 with a temperature of 70.4 degrees, according to Jan Null, a meteorologist with Golden Gate Weather Services.

For most of the Central Valley and California, July and August are when temperatures peak and folks experience the hottest day of the year. Sacramento’s warmest day of the year is typically on July 20, with a whopping 93 degrees. San José’s is on August 29 at 81.9 degrees, and Los Angeles on August 27, with a steamy 84.8 degrees.

Why the Bay Area is behind on summer’s schedule

Here in the Bay Area, we live in a Mediterranean climate, a climate with a combination of hot, dry summers and mild wet winters, according to Null. “A fairly unique area as far as temperature goes,” he said.

Fog settles over San Francisco Bay, with the Golden Gate Bridge, Coit Tower and the Bay Bridge visible in the distance. (Brocken Inaglory/Wikimedia Commons)

In the summertime, the Bay Area is dominated by an area of high pressure over the state’s coastline called the North Pacific High. In the Central Valley, on the other hand, where the sun heats the valley floor, hot air rises and creates an area of low pressure.

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Air flows from an area of high pressure to low pressure, it forms what we know as the Bay Area’s sea breeze. “We’ve been kept cool by the sea breeze and natural air conditioning from the ocean all through the summer,” said Null.

In the fall, the sun’s path gradually shifts farther south as we approach the equinox, and that North Pacific High pressure becomes less dominant. The marine layer fades and our natural air conditioning — that nice sea breeze — either lessens or goes away. At this point, winds can sometimes blow in reverse, from the interior to the coast bringing hot, dry air also known as the Diablo wind — Northern California’s version of the Santa Ana winds that rip across the southern part of the state.

How will climate change impact the Bay Area’s ‘second summer’?

Coastal area temperatures are dictated by ocean temperatures. And while the ocean is warming off the coast of California, it isn’t warming enough to dramatically change the summertime weather pattern.

For San Francisco, the average fall day may be a bit warmer — but not excessively so, said Michael Wehner, a senior scientist at the Lawrence Berkeley National Laboratory.

“My fearless prediction is that fall will remain its nicest weather,” joked Wehner.

But Wehner says that we should caution that little is known about how coastal fog will change, if at all, as the planet warms. Some research suggests that fog is decreasing in California but the reasons aren’t entirely clear. And there are other climate threats facing the Bay Area, namely sea level rise and much more intense winter storms.

A view of tall redwood trees seen towering above.
Reinhardt Redwood Regional Park. Sprawling forest featuring redwood groves and rare wildlife, plus trails, picnic areas and campsites. (John Hudson Photography/Getty Images)

I want to find cool temperatures for true fall vibes. Where can I go in the Bay Area?

Think: coastal, shaded, elevated.

This time of year, if you want to escape the heat, the best place to go is toward the coast rather than inland. Even though we’re warming up on the coast without as much fog, we’re still surrounded by a “big pool of water” called the Pacific Ocean with temperatures that are in the 60s, says Null.

Null recommends that if you’re looking to escape the heat in search of some brisk fall temperatures, you should hit the coast — like areas in Marin County — or go to higher elevations, like in the foothills of the Sierra.

Divya Konda is founder of Weekend Wanderers Inc., a social media space recommending different hikes around the Bay Area. And for chillier fall hikes, Konda recommends heading over to Marin County to places like Point Reyes National Seashore and Muir Woods.

Point Reyes National Seashore from Chimney Rock trail at sunset in the winter of 2021. (Conrad J Camit/Getty Images)

To enjoy some of the best redwood trails in the Bay Area, Konda also suggests heading over to Purisma Creek Redwoods. And on the Peninsula, Konda recommends Cowell Purisima Coastal trail, a pleasant ocean-side trail that’s best enjoyed on a clear day. “The gentle breeze and the ocean views are easy to fall in love with,” says Konda. While you’re on the Peninsula, Half Moon Bay State Beach is another great spot to find cool coastal trails.

In the South Bay, Konda recommends another hidden gem that the locals love: The Sanborn Creek Trail, that’ll take you by the bustling creek, and is completely shaded.

In the East Bay, a favorite among Bay Area residents and a recommendation by Konda to escape the heat is Reinhardt Regional Park. Most of these redwoods are second- or third-generation redwoods and the park offers some great trails to hike, says Konda.

These recommendations might be great places to visit to escape the heat, but of course they’re also hiking gems that can be enjoyed throughout the year.

Where to go to find warmer weather?

A little later in the fall in November, when cooler, autumnal temperatures finally hit the Bay Area, you might then be looking to spend time in warmer temperatures.

Some of the warmer spots in or near the Bay Area, Null advises, are farther away from the coast into the Tri-Valley area.

The more inland you go, the warmer the temperatures will be. Some recommendations are to go inland into the lower peninsula for hikes at places like Russian Ridge Preserve or Castle Rock State Park.

You might also want to stick to lower elevations and trails more exposed to the sun (but don’t forget that sunscreen!). Redditors also recommend trails that involve ridges and peaks when the weather is clear and warm.

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At KQED News, we know that it can sometimes be hard to track down the answers to navigate life in the Bay Area in 2023. We’ve published clear, practical explainers and guides about COVID, how to cope with intense winter weather and how to exercise your right to protest safely.

So tell us: What do you need to know more about? Tell us, and you could see your question answered online or on social media. What you submit will make our reporting stronger, and help us decide what to cover here on our site, and on KQED Public Radio, too.

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