Glen Ellen Weather

April and May are your ideal months for Glen Ellen. April brings excellent weather with highs around 76°F, 12.8 hours of daily sunshine, and almost no rain. May is even better at 79°F with 12.9 hours of sun and virtually perfect conditions that produce a 93 comfort score. These spring months align with Sonoma Valley's most pleasant season, when the vineyards are in full leaf and outdoor activities are at their peak. Summer months like July and August are warmer (reaching mid-80s) but have slightly more morning fog. If you prefer milder weather for walking, spring is unbeatable. Just note that these peak months can draw crowds to the wine tasting rooms and outdoor patios.

Glen Ellen runs significantly warmer than coastal areas like San Francisco or Marin. The town's average high of 72.5°F is 10-15°F warmer than the coast year-round, and during summer peaks, Glen Ellen reaches 86-87°F while the coast stays stuck in the 60s. This difference sharpens in fall and spring. October in Glen Ellen averages 65°F, while coastal towns struggle with 55°F. The Sonoma Valley's inland position creates a clear microclimate: it's protected from marine layer fog that blankets the coast and receives more direct sunshine. If you're escaping coastal fog and seeking actual warmth, Glen Ellen delivers. Learn about the Bay Area's microclimates to understand why nearby destinations vary so much.

Glen Ellen experiences modest morning fog compared to most Bay Area towns. You'll see about 1.6 hours of fog per day on average, with the most fog in October (3.4 hours) and November (3.2 hours). That's notably less than coastal Marin or San Francisco, which can have 4-6 hours of morning cloud cover. Spring and early summer see the least fog (0.7-0.8 hours), making those months crystal clear. The valley's position gives it a weather advantage: morning fog typically burns off by mid-morning, leaving you with full sunny afternoons. If you're planning outdoor wine tastings or hiking, plan for the first hour or two to be cool and potentially overcast, but expect beautiful clear conditions by lunchtime. Understand how Bay Area fog forms and why some locations get more than others.

Glen Ellen's temperature range is moderate for the Bay Area. Peak warmth arrives in July and August when highs routinely hit 86-87°F with lows around 56-58°F. That's warm and pleasant, not scorching. Winter lows drop to the low 40s (December through February see lows of 40-43°F), but daytime highs stay in the upper 50s to low 60s. You won't experience the 90+ heat days that inland areas see, nor the freezing conditions of high elevations. This relatively gentle climate is partly why Glen Ellen became popular for wine growing and weekend getaways. The comfort index reflects this consistency, hovering in the high 80s during summer peak and staying above 65 even in the wettest winter months. Layer your clothing from October through March when mornings and evenings can feel cool.

April through October are prime outdoor tasting season in Glen Ellen, with April-May and September being the sweet spot. April peaks at 76°F with 12.8 hours of sunshine and virtually no rain, while May hits 79°F with equal sun and a 93 comfort score. Both months are warm enough for shirtsleeve weather but cool enough that you won't overheat while walking between tasting rooms. June stays pleasant at 79°F, though you'll notice slightly more morning fog (1.7 hours). July and August are hot (mid-80s) but dry and mostly cloudless. September dips to 72°F, offering that perfect goldilocks temperature. October begins to cool to 65°F, but it's still enjoyable with 7.1 hours of daily sun. Winter months (November-February) bring rain and cooler weather (59-60°F highs), making outdoor patios less appealing. Dress appropriately for varying temps even on pleasant days.

Glen Ellen receives about 78 rainy days per year with roughly 41 inches of annual rainfall, concentrated from October through March. The worst months are January (nearly 10 inches) and October (over 9 inches), followed by November with 8.67 inches. December through February bring consistent rain and cloud cover. Spring (March through May) is notably drier, with April seeing just 0.22 inches and May bone-dry at zero rainfall. Summer is nearly rainless from June through August. If you're planning a visit and want to avoid wet weather, target April through September. The rainy season can last weeks at a time, especially December through February. Morning fog is more persistent in these months too. However, the rain creates lush green vineyards and produces Glen Ellen's award-winning wines, so there's something beautiful about visiting during shoulder months like March or October when rain is tapering off.

Pack layers, even in summer. Morning fog means starting cool (50-60°F) regardless of season, with afternoons warming 15-25°F by midday. In April-May, bring a light jacket, t-shirts, and comfortable walking shoes. Summer (July-August) calls for short sleeves, sunglasses, and sunscreen, but keep a sweater for early mornings and air-conditioned tasting rooms. Fall (September-October) is similar to spring, though October can turn rainy, so add a rain jacket. Winter (November-February) requires more layers: a fleece, waterproof jacket, and long pants. The key is versatility, not bulk. Glen Ellen's inland valley position means you get more direct sun than coastal areas, so sunscreen and a hat are smart year-round. Comfortable walking shoes matter since you'll stroll between tasting rooms and maybe explore local parks. If you're visiting in winter, waterproof shoes beat sneakers.

Glen Ellen sits in the Sonoma Valley interior, which gives it relative shelter from the fiercest Bay Area winds. The town averages moderate conditions, rarely experiencing the sustained gusts that pummel coastal ridges. However, Sonoma County does sit in the path of atmospheric rivers, particularly from November through February. During these months, heavy rainfall arrives with strong winds, creating challenging weather. October 2024 and January 2025 both brought over 9 inches of rain, some arriving in concentrated bursts. Winter storms can turn roads slick and reduce visibility for hours. Spring months (March-May) are reliably calm and dry. If you're planning outdoor activities, avoid December through February for wind and storm risk. Learn about atmospheric rivers and how they shape Bay Area winter weather. The upside is that Glen Ellen's Sonoma Valley location means it avoids the relentless coastal wind that characterizes bay-adjacent areas.

Glen Ellen sits right in the heart of Sonoma Valley wine country, flanked by nearby towns that each have subtle weather differences. Kenwood is just north and sits slightly higher in elevation, which keeps it a few degrees cooler year-round. Sonoma town proper sits in the valley floor, experiencing nearly identical weather to Glen Ellen. The real weather variation comes from elevation and distance from the coast. Glen Ellen's 220 feet elevation is low enough to avoid the coolness of foothill locations, but high enough to escape marine layer fog. All three towns share the spring warmth and winter rain pattern. For outdoor activities, they're functionally equivalent from a weather standpoint. Your choice should depend on tasting rooms and restaurants rather than weather. However, if you explore nearby ridge-top parks like Jack London State Historic Park or Sugarloaf Ridge State Park, expect noticeably cooler temperatures due to elevation.

Glen Ellen's dry season runs clearly from May through September, with June-August being the most reliably rainless. May averages zero rainfall and June just 0.09 inches, making them virtually guaranteed dry. July through August see minimal rain too (0.04-0.14 inches). This five-month window is when you can confidently plan outdoor events without weather backup plans. April bookends spring nicely with just 0.22 inches of rain. September sees more variability (2.56 inches), signaling the transition to wetter months. October through March should be considered wet and uncertain, with October through January particularly rainy. The best confidence for dry weather is June through August, when you're looking at single-digit rainfall probabilities. April and May offer excellent weather with slightly higher backup-plan risk. If you're coordinating group outings, wine harvest events, or outdoor activities, June-August and April-May are your surest bets.

Glen Ellen gets substantial direct sunshine averaging 9.4 hours per day across the year, which is excellent for a Bay Area location. The peak sun arrives from April through July, when you get 12.1-12.9 hours daily. This puts Glen Ellen squarely in the Bay Area's sunniest tier. By comparison, coastal towns lose 2-4 hours daily to marine layer fog and cloud cover. Winter months see the least sun (5.8-6 hours in November-December), but even that's reasonable. October dips to 7.1 hours as fall clouds arrive. The abundance of sun in spring and early summer is why Glen Ellen's comfort scores climb into the 90s during April and May. That consistent sunshine throughout the year helps the region's wine grapes ripen beautifully, and it means you'll rarely feel stuck in perpetual gray skies. If you're escaping coastal dreariness, Glen Ellen's Sonoma Valley location delivers genuine sunny days year-round. Just note that winter sunshine comes at a lower angle, which means mornings and evenings stay cool.