Mt. Tamalpais East Peak Weather

September is the best month to visit Mt. Tamalpais East Peak for views and comfortable hiking. The fog frequency drops to just 0.7 hours per day, temperatures sit in the low-to-mid 70s at the peak of the day, and the marine layer has weakened enough that the summit typically stays clear through the afternoon. Comfort scores reach 85 out of 100. June and July are nearly as good, with comfort scores also at 86 and sunshine averaging 11 to 12 hours a day, but those months carry a higher chance of morning fog that can temporarily obscure the panoramic views. What makes September stand out is the combination of long clear windows, the last of the summer warmth, and the absence of the heavy marine push that characterized the earlier summer months. October drops off noticeably, with lower temperatures and rain beginning to appear, though the fall air clarity can produce some of the sharpest, most dramatic views of the year on dry days. For a reliable all-day clear summit, September wins. For the iconic fog-sea-below-your-feet experience, July mornings are hard to beat. See our guide to the best months for hiking in the Bay Area for more detail on seasonal patterns across the region.

The East Peak averages a low of 47.8°F across the year, but winter mornings regularly dip into the low 40s, and January and February bottoms sit around 43°F. At 2,571 feet, the summit is consistently 10 to 15 degrees colder than the towns directly below, so a mild 60°F afternoon in Mill Valley can translate to a brisk 45 to 48°F at the peak, especially once wind is factored in. Wind chill is a real consideration here. The summit is fully exposed, and even moderate Bay Area winds of 15 to 20 mph can make temperatures feel 8 to 10 degrees colder than the thermometer reads. November through January is genuinely cold, with highs in the mid-50s and lows in the mid-40s, and wet cold when rain arrives. The elevation also means the peak is occasionally dusted with frost on the coldest winter nights, though significant snow is rare. Even in summer, once the sun drops toward the ridge in late afternoon, temperatures fall quickly. July might see a high of 72°F at midday, but by late afternoon the wind picks up and 55°F is not unusual. Read more about how wind chill works in the Bay Area to understand how exposed summits like East Peak feel significantly colder than forecasts suggest.

Yes, most of the time in summer. The summer marine layer over the Bay Area typically has a ceiling between 1,500 and 2,000 feet, which puts the East Peak at 2,571 feet comfortably above it on a typical morning. When conditions are right, you drive up through the fog bank on the lower slopes and emerge into full sunshine at the summit while the entire Bay sits under a flat white lid of cloud. It is one of the more dramatic weather transitions in the Bay Area. That said, "above the fog" is not a guarantee. On strong marine push days, the fog climbs above 2,571 feet and the summit disappears into cloud by late morning. June and July see about 1.2 to 1.5 hours of fog per day at the summit on average, meaning these events happen but do not dominate. May is the foggiest month at East Peak, averaging 2.2 fog hours per day, as the marine layer is often at its deepest then. September, by contrast, averages just 0.7 fog hours per day and is the most reliably above-fog month of the year. The relationship between elevation and fog in the Bay Area is a genuine pattern here, not just a nice story.

Late morning to early afternoon is the most reliable window for clear views from East Peak, roughly 10 a.m. to 2 p.m. In summer, the marine layer is often at its thickest in the early morning hours, so arriving at dawn does not always deliver the clearest views, though it can produce the famous sea-of-fog spectacle if the summit is poking above the cloud ceiling. As the day warms, the marine layer typically retreats, and by late morning the views are usually at their most open. Afternoon is the sweet spot: fog has cleared, visibility is high, and the sun angle is good for seeing across the Bay, east toward the Sierra, and south toward San Francisco. By late afternoon, wind picks up and temperatures drop, so the viewing window starts to close from a comfort standpoint even as the light turns golden. In fall and winter, the fog question largely disappears and midday visits are simply the warmest and clearest. Avoid early morning visits during May and June if your primary goal is unobstructed views rather than the fog experience. If you want both clear views and the fog spectacle, aim for a summer morning arrival around 8 a.m. and stay through late morning to watch the transition.

East Peak is exceptionally sunny for a Bay Area location, averaging 9.8 hours of sunshine per day across the full year. In peak summer, June delivers 12.5 hours of daily sun and July averages 11.8 hours. Even September, as the days begin to shorten, still averages 9.5 sunshine hours. This is partly a function of the elevation: at 2,571 feet, the summit sits above the marine layer ceiling on most summer days, so while the fog is blocking the sun in San Francisco and along the Marin coast, East Peak is in full sunshine. The temperature inversion that traps the marine layer below the summit is the same mechanism that makes the summit so sunny. Winter months drop significantly, with the shorter days and more frequent overcast from storm systems, but even then the elevation helps the summit see more sun than the foggier coastal locations at sea level. The practical implication for hikers is that East Peak carries a genuine sun exposure risk in summer despite its location in a famously foggy metropolitan area. Sunscreen and a hat are not optional here, especially on the fully exposed summit trails.

Layers are non-negotiable at East Peak. The summit is exposed and 10 to 15 degrees colder than the towns below, and the wind makes it feel colder still. Start with a moisture-wicking base layer, add an insulating mid-layer, and bring a windproof shell even if you leave the car in short sleeves. A light fleece or puffy jacket fits in a daypack and will feel essential the moment you reach the exposed ridgeline, even on warm summer days when Mill Valley is at 75°F. The Bay Area's layering demands are well documented for the coast, but the summit takes them further because the temperature drop is more abrupt and the wind has no obstacles. Beyond clothing, bring sunscreen and sunglasses: the summit gets real UV exposure, and the sun reflecting off fog below you adds to it. In winter and early spring, waterproof footwear matters. Trails can be muddy from October through March, and rain arrives with little notice at elevation. Trekking poles are useful on wet trails. Pack water regardless of season; the cool temperatures at the summit make it easy to underestimate how much you are sweating on the ascent.

The rain season at East Peak runs roughly October through April, with November, December, and January being the wettest months. The Marin watershed, which the mountain anchors, is one of the rainiest areas in the entire Bay Area due to orographic effects: storms approach from the Pacific and are forced upward against the mountain terrain, cooling and dropping disproportionate rainfall on the way up. Nearby Kentfield averages 50 to 55 inches of annual rain, more than double San Francisco's total, and the mountain itself gets even more. November averages around 8 inches of rain. December varies widely, anywhere from 1 to 4 inches in dry years to much more in wet ones. January is another high month at roughly 8 inches. March dries out quickly, averaging just 0.5 inches, and April drops to 0.2 inches. May through September is genuinely dry, with essentially no measurable rain. October is transitional, averaging around 5 inches as the first storms of the season arrive. For hikers, the message is clear: late October through early April means wet trails, possible mud, and the need for rain gear. March and April offer a sweet spot where the hills are green, waterfalls are running, rain has mostly stopped, and the summer crowds have not arrived.

East Peak in summer is often sunnier, cooler, and less foggy than the coastal towns nearby, which is a counterintuitive combination. Stinson Beach, just a few miles west at sea level, can be completely fogged in during the summer marine push while East Peak sits in sunshine 500 feet above the marine layer ceiling. At the same time, East Peak runs 5 to 10 degrees cooler than the warmer inland East Bay cities. July temperatures at East Peak average a high of 72°F, which is warmer than San Francisco's foggy summer and cooler than Walnut Creek or Livermore. The elevation creates a genuine sweet spot: above the marine layer for sunshine, but high enough to escape the 90 to 100°F heat that bakes the inland valleys. Comfort scores at East Peak in July reach 86 out of 100. The Bay Area's extraordinary microclimate diversity is on full display when you compare East Peak to locations just a few miles away. Muir Woods at the base of the mountain can be 10 to 15 degrees cooler and fogged in while the summit is warm and sunny. The elevation gradient here compresses weather changes that would normally require driving 50 miles.

Yes, East Peak is genuinely windy, and the exposure is a significant factor in how the summit feels. The peak sits at 2,571 feet with 360-degree exposure, which means there is nothing to buffer the prevailing northwest winds that dominate Bay Area summer afternoons. Wind speeds at the summit regularly run well above what is recorded in the towns below. The afternoon marine push that brings cool air into the Bay from the Pacific hits the mountain directly, and the summit gets the full force of it. This is the same wind pattern that makes San Francisco feel cold in July, but at elevation and without any shelter, the effect is more pronounced. Read more about why the Bay Area is so windy to understand the broader pattern driving summit conditions. The practical implication: even if the thermometer says 68°F, a 20 mph wind can push the feels-like temperature into the upper 50s. Morning visits are generally calmer than afternoon visits. The wind picks up most noticeably after noon as the marine layer strengthens its onshore push. In fall and winter, storm winds at the summit can be strong enough to make standing at the viewpoints uncomfortable. The wind is also part of what makes the summit views so dramatic, the air is clean, clear, and constantly moving.

November and December are the least comfortable months at East Peak, and the data supports this clearly. Comfort scores drop to 64 to 68 in November, the lowest of the year, and December ranges from 60 to 80 depending heavily on whether the month is wet or dry. November averages around 8 inches of rain, the highest monthly total, and highs sit in the mid-50s with lows in the mid-40s. At elevation, these temperatures are noticeably colder, and wet conditions on exposed trails make the experience genuinely unpleasant for most visitors. January is not much better, with another 8 inches of average rainfall and the same temperature range. The Bay Area's rainy season peaks in January overall, though for the mountain specifically November is the competitor. That said, even winter at East Peak has redeemable moments. After a storm clears and a high-pressure ridge settles in, the summit can deliver some of the clearest views of the year, with snow on the Sierra visible to the east and the entire Bay laid out in crystalline detail. These clear winter days are just less predictable and surrounded by a lot more gray. If you visit in November or December, pick a day after a storm clears and dress for temperatures 15 degrees colder than the forecast.