There's a reason why you will see loads of people walking around wearing Fisherman's Wharf fleece pullovers, they didn't read up on the weather before they came to San Francisco! September is one of the warmer months here and I wore mine quite frequently in the evening, I was even a little chilly wearing it on the way back from Alcatraz at night.
And although there's no evidence that Mark Twain ever said "The coldest winter I ever spent was a summer in San Francisco" there's a reason why it is oft quoted, temperatures above 80F are considered a heat wave and the average high temperature in June, July and August is 66-67F with lows in the mid 50s, winds off the bay can also create a wind chill that makes it feel even colder.
Don't Get Blown Away!
Being on the coast, San Francisco knows how to kick up a good wind. It is not uncommon for a strong wind to be present on an otherwise warm day. Don't be surprised if you are faced with the choice of wearing a jacket and boiling over or getting blasted by wind. Some locations are more likely to get windy; such as, Downtown and the Financial District where the high rises create wind tunnels, Civic Center (near Market Street and Van Ness Avenue), Ocean Beach, the Marina, Twin Peaks, and the deck of the Golden Gate Bridge. Due to the City's microclimates, it is common for one neighborhood to experience gusty winds while a nearby neighborhood has dead calm. You may want to bring a jacket when you head out on the town.
If you are planning to spend the whole day and night exploring the city, beware that temperature can drop very fast night.
Depending on the time of the year and changing bay weather conditions, you can be fine with T-shirt in the sunny morning and then shivering at night if you do not bring a warm jacket.
So better carry a sweater or jacket, then be sorry. Of course, it is great excuse to buy new clothes if you have some money to spend.
...was a summer in San Francisco. - Mark Twain
When I first moved to San Francisco, I thought people were joking. But they weren't. It can actually get pretty chilly during the summer in San Francisco. If you are coming during the summer, bring a jacket! Otherwise, you will just end up buying something here to keep you warm.
No Matter how beautiful the day begins, it will get cold by 2 or 3 o'clock. Always have a sweatshirt or flannel or something with you. The wind is cold and strong. some of us love it this way, but it is not typical american summer weather and will catch the unsuspecting off-guard. Locals do not buy San Francisco sweatshirts. It's an advertisement you got caught unawares and it's the reason there are sweatshirt vendors every 2 feet. ;>)... The winter is rainy, the summer is dry, but cold and foggy. Warmest month is probably September, with little mini summers in late june.
It generally is NOT hot in the summer months. Be prepared for many, many foggy days in July and August. Of course, on the east side of town the fog usually burns off by mid-day, but it can just as easily roll back in late afternoon. You will not need a winter coat, but I do recommend a light jacket for the day, and then a warmer jacket (like leather) for night.
The photo accompanying this tip was taken on June 30, 2005, from the roof of my apartment. As the news reports were providing heat warnings for the inland areas and giving people advice on how to keep themselves safe during days of extreme heat, this is what it looked like right next to the Golden Gate Bridge at 4:00pm. It was approximately 30F degrees cooler in San Francisco than it was less than 30 miles away.
It was a beautiful morning, so I walked to work without a jacket, and...well, you know how this story goes. I was invited to dinner at a restaurant on Fishermans Wharf, where it always seems to be colder than the rest of the city. And, yes, it got too cold. So, yes, I had to spend $13 on a sweater I didn't really need :-(
My mistake: I took the SF weather for granted. How much money do these souvenir store owners make on people like me?
In San Francisco, sometimes it's both hot and cold at the same time. It seems to depend on whether you're in the sun or shade-the sun's too hot, the shade's too cool.
Going out here, I tend to overdress-you can always take something off. Besides, I really don't want to spend money on a sweatshirt at Fisermans Wharf if I can help it. Nights can be especially chilly.
My advice on dressing here is...well, I really don't have any-if I can't figure it out myself, why would you listen to me!
Still, it beats being home in the winter! :-)
be sure to wear your deodorant during this time of the year especially if taking the public transportation - cable cars, etc...
i did smell some plentiful armpits during a public transportation ride. one incident was when this man raised his arms to hold on to the rails. i was sitting down while he was above me - he was wearing a 'wife beater shirt' (sleeveless) and whey!!! the smell was so terrible!!! and since public trans is also used by transients found in the area...
The day can start out hot in Pacifc Heights, and by 2pm be absolutely freezing on the Golden Gate Bridge. The winds come off the water and make it really cold and uncomfortable rather quickly. Dresss in layers and always bring a jacket and more sweaters than you think you need. In the afternoons and evenings it starts to get cold. The Golden Gate bridge can be freezing with it's windy conditions even on a lovely day. Fishermans' wharf can also be cold due being right on the water.
San Francisco has pleasant weather for the most part, but it can get pretty windy here. During the winter it can also get pretty cold, and with the wind it can get really cold. But it rarely snows in the San Francisco Bay Area, so you don't have to worry about that. During the summer you can thank the sea breeze that makes San Francisco the "Air Conditioned City". Just to give you an example, during the summer the temperature in the Bay Area can be about 50-60 degrees F, while just inland (say in Sacramento the temperature can reach over 90 degrees F). That being said, there are days during the summer when the Bay Area can be pretty hot due to an offshore wind.
Part of the lore and romance of San Francisco is the fog, but it can play havoc with your photography plans. It can also be dangerous for your travel plans. Flying and driving can be risky in heavy fog, so be careful.
Visitors gazing at palm trees in photo albums of San Francisco may be surprised to learn that it is far from a subtropical paradise. Contrariwise, it can become quite cold and views well-obscured by a dense fog which rolls in during the late afternoon and lifts by morning, though it tends to linger closer to the ocean and on the Bay itself. Certain neighbourhoods, mostly on the city's east side, are more prone to sunshine than others. The Sunset in particular seems to be perennially fogged-in. Don't expect uninterrupted vistas or perfect, cloudless days to necessarily await your trip to San Francisco.
The San Francisco fog has quite a reputation and it is well deserved. It is thick. It is moist. And it will blind you instantaneously especially if you are driving through it. It is pretty though. This shot was taken of the Golden Gate Bridge. Imagine what it was like for the cars on the bridge.
San Fransisco might sound like a warm and hot place, but I went there and I found out that its cold in the mrning and at night. So if you plan to get up and spend the whole day outside, I advise you to get like some kinda light jacket cause it can get kinda warm in the afternoon, and when you sleep, use some covers or blankets. Hope this advice helps you and most importantly, HAVE FUN!!!!