Stinson Beach Weather

September is genuinely the best month at Stinson Beach. The summer fog that blankets the coast in June and July has largely retreated by then, fog averages drop to just 0.9 hours per day, and temperatures climb to highs around 76°F, making it feel more like a proper beach day than most of summer. The comfort score hits 87 out of 100, matching July and August, but with noticeably better sun and less wind. June, July, and August are all excellent too, with highs in the mid-70s and comfort scores of 87 to 88, but they come with more marine layer activity in the mornings. If you want the sweet spot of warm air, calm fog, and long daylight hours, September wins. April and May are sleeper picks as well, with comfort scores of 82 to 85 and very little rain. Just do not count on October: temperatures drop into the low 60s and rain starts showing up. For a full breakdown of how Stinson Beach weather shifts through the year, see our Stinson Beach weather guide.

Not as hot as you might expect, which surprises a lot of first-timers. Summer highs at Stinson Beach run in the mid-70s: 76.5°F in June, 74.9°F in July, and 74.1°F in August. Lows stay in the mid-50s all summer. That is legitimately pleasant beach weather, but it is not Santa Cruz or Southern California heat. The ocean water stays cold year-round, typically in the low-to-mid 50s°F, so the air temperature is rarely the limiting factor for comfort. The bigger variable is the marine layer. On mornings when fog rolls in thick from the Pacific, the beach can feel 10 to 15 degrees cooler than the thermometer suggests, especially with any wind. By early afternoon most days, the marine layer burns off and direct sun pushes the perceived temperature up considerably. The beach faces southwest, which gives it excellent afternoon exposure. Bring a light jacket for the morning regardless of what the forecast says. See our guide to Bay Area ocean water temperatures if you are wondering what to expect in the water.

Yes, but it is manageable. Summer is actually peak fog season along this stretch of Marin coast, driven by the same pressure patterns that cool San Francisco every June. At Stinson Beach, fog averages about 2.1 hours per day in June, drops slightly to 1.7 hours in July, then ticks back up to 2.3 hours in August. That is mostly morning fog, and on most days it burns off by mid-morning to early afternoon. September is the clear standout: fog drops to just 0.9 hours per day on average, making it the sunniest month of the year at Stinson. May actually has the highest fog average in the data, at 2.7 hours per day, which is part of why it gets overlooked even though rain is nearly zero. The fog at Stinson tends to sit right on the coast and can be thicker than what you would find a few miles inland. If you drive over from Mill Valley on a foggy morning and the beach is socked in, waiting an hour or two usually resolves it. For the science behind why summer fog peaks here, see why Bay Area fog is most intense in summer.

On a typical summer morning, the marine layer at Stinson Beach starts clearing between 10 a.m. and noon. That window shifts by month and by how thick the fog came in overnight. In July and August, when the pressure gradient between the hot Central Valley and the cold Pacific is strongest, fog can hang around until 1 or 2 p.m. on some days before finally breaking. September mornings tend to clear faster, often by 10 a.m., which is one of the reasons that month feels so much more reliably sunny. The beach faces southwest, which means it catches afternoon sun well once the fog clears, and the light stays good well into the evening. A practical approach: check the satellite imagery in the morning before you leave. If you can see a solid white band sitting right on the coast, plan to arrive by noon rather than 9 a.m. If the coast looks clear in the morning satellite image, you are usually in great shape from arrival. Understanding how morning fog forms in the Bay Area makes it easier to predict what you will find when you arrive.

It can be, particularly in the afternoon. Stinson Beach sits at the mouth of a valley that opens toward the ocean, and the sea breeze picks up reliably most afternoons from late spring through early fall. By 2 or 3 p.m. on a warm, sunny day, wind at the beach can be brisk enough to blow umbrellas and scatter napkins. This is classic coastal California behavior: warm air rising inland draws cool marine air onshore, and the effect strengthens as the day heats up. Morning hours are almost always calmer, which is another reason the beach has a different character before noon than after. October and November bring storm-related wind that is less predictable and colder. For beach days, the sweet spot is often late morning to early afternoon, after the fog has cleared but before the afternoon wind fully kicks in. Nearby Muir Beach tends to be slightly more sheltered from direct afternoon wind due to its cove orientation, which is worth knowing if wind is a dealbreaker for you.

September is the warmest month at Stinson Beach, and it is not particularly close. Average highs hit 76.2°F, slightly above the June peak of 76.5°F and meaningfully warmer than July and August. More importantly, the fog that suppresses temperatures in early summer is largely gone: fog averages just 0.9 hours per day in September, compared to 1.7 to 2.3 hours in July and August. That means the sun actually delivers its full effect rather than burning through a haze all morning. Lows stay comfortable at 57°F. The comfort score of 87 out of 100 ties with July and August, but many visitors find September the most pleasant in practice because the sun is reliable and the wind tends to be lighter than in peak summer. Rain is minimal in September, averaging 0.36 inches for the month. This pattern of September being hotter than July is a well-known Bay Area quirk, and it applies strongly along the Marin coast. If you have flexibility in your schedule, a September weekend at Stinson is about as good as the beach gets in Northern California. See why September is hotter than July in the Bay Area for more on the underlying pattern.

Layers are not optional at Stinson Beach, they are the whole strategy. Start with a swimsuit or light layers as your base, add a long-sleeve shirt or light fleece for the morning, and bring a windproof outer layer you can stuff in a bag. The temperature difference between a foggy 9 a.m. arrival and a sunny 2 p.m. beach session can easily be 15 degrees, sometimes more. Even on days when the forecast shows 75°F, the beach itself can feel significantly cooler if there is wind off the water. Sunscreen matters more than most people expect at Stinson: even on partly cloudy days, UV exposure at sea level with reflective sand and water is high, and the mild temperatures can make you forget how much sun you are getting. Bring more layers than you think you need in May and June, which have the highest fog averages of any month. In September, you can probably get away with less, but a jacket for the return drive is still worth having. Sandals work for the beach, but the parking area and nearby town involve actual walking, so footwear with some grip is smart. The layering logic that applies here applies to most Bay Area coastal spots. See why San Francisco weather demands dressing in layers for the full reasoning.

The rainy season runs from November through February, with October being a transitional month where precipitation starts picking up and the long summer dry spell ends. November and January are the wettest months, each averaging around 8 to 8.5 inches of rain. February averages 3.86 inches and December varies considerably from year to year, ranging from 1 to 4 inches depending on the storm track. By March, the pattern starts improving fast: rainfall drops to 0.52 inches and the comfort score jumps to 81 out of 100. April brings it down further to 0.21 inches, and May is nearly dry at 0.02 inches. June through August sees essentially zero rain at Stinson, with July averaging just 0.12 inches and August 0.07 inches. Stinson Beach sits in coastal Marin, which catches significant moisture from Pacific storms, so annual rainfall here is higher than in many parts of the Bay Area. The roughly 79 rainy days per year are concentrated almost entirely in those four wet months. For context on how this fits the broader Bay Area rainfall pattern, see the rainiest month in the Bay Area.

Yes, and the differences are sharper than the distances suggest. Stinson Beach, Bolinas, and Mount Tamalpais State Park are all within a few miles of each other, but they can have completely different conditions on the same afternoon. Stinson and Bolinas sit at sea level right on the coast, so they share similar fog exposure, marine air, and afternoon sea breeze. The distinction between them is subtle: Bolinas sits slightly more sheltered in its lagoon position and can be a degree or two warmer on clear days. Mount Tamalpais, at nearly 2,600 feet, operates on a completely different weather logic. It is often above the fog layer that sits on the coast below, meaning you can be in full sun at the summit while Stinson is foggy. In summer, the summit can actually be warmer than the beach in the afternoon because the fog has not reached that altitude. In winter, the mountain gets significantly colder and wetter than the coast. The Bay Area's microclimate variation is genuinely striking, and this corner of Marin is a good illustration of how dramatically conditions change over short distances. The Bay Area microclimates guide explains the underlying geography.

Stinson Beach averages around 225 days per year that qualify as good weather by reasonable standards, and sunshine averages 9.4 hours per day across all months. The sunniest months are June through September, with June leading at 12.4 hours of sunshine per day and September close behind at 9.3 hours. That is a lot of sun, and the fog that does appear tends to be a morning phenomenon rather than an all-day event. October starts the transition toward shorter days and more overcast conditions, and November and December are the cloudiest months by a significant margin. Even in winter, though, Stinson gets clear days. The December comfort score varies widely, from 62 to 82 in the data, which reflects how variable winter can be: a string of storm days followed by a beautiful clear week with highs in the 60s is completely normal. The beach faces southwest, which gives it excellent afternoon light even on shorter winter days. For beach trips specifically, planning around the June through September window gets you the most reliable sun. That window represents the bulk of those 225 good-weather days, with the rest scattered through spring and occasional winter breaks in the storms.