Calistoga Weather

Calistoga is the hottest and sunniest town in the North Bay wine country, sitting at the northern end of Napa Valley at 362 feet elevation. The average high is 73.6°F year-round, but that number obscures the real story: summers are genuinely hot, with July and August highs reaching 90°F or above, while winters are mild at 57-61°F. The town averages 9.6 hours of sunshine per day and just 1.3 hours of morning fog, which makes it dramatically sunnier than anywhere on the coast. Annual rainfall runs around 38 inches, concentrated almost entirely in the November through April window. By Bay Area standards, Calistoga is a warm, dry refuge. It earns an annual comfort score of 83 out of 100 and racks up roughly 281 perfect weather days per year. If you want warmth, sun, and minimal fog, this is one of the most reliable spots in the region. You can dig into the full seasonal picture at the Calistoga weather guide.

May, April, and June are the top three months, in that order. May delivers the ideal combination: average highs around 80°F, over 13 hours of daily sunshine, virtually no rain, and negligible fog. It sits right before the full heat of summer arrives, so you get warm, clear days without the intensity of July and August. April is a close second, offering pleasant temperatures around 73°F with the valley still green from winter rains. June is excellent too, though temperatures start climbing toward the upper 80s. If you can tolerate heat, July and August are spectacular in terms of sunshine and clarity, just be ready for 90°F afternoons. September is an underrated month: temperatures moderate from peak summer, the vine leaves turn golden, and rainfall remains nearly zero. The worst stretch runs December through January, when highs drop to 57-59°F and rain is almost guaranteed. Learn more about how the Bay Area's seasons actually play out to plan your visit around the conditions you prefer.

Very hot. Calistoga sits at the top of Napa Valley, sheltered from marine cooling by surrounding ridges, and it bakes throughout the summer. July and August regularly see highs in the 90-95°F range, with occasional heat waves pushing temperatures above 100°F. This is a full 15 to 20 degrees warmer than the San Francisco coast on the same day. The mechanism is straightforward: the valley floor heats rapidly under the strong summer sun, and the surrounding hills trap that warm air rather than letting Pacific breezes sweep it away. Mornings remain cool, typically 55-60°F, so the temperature swing from dawn to afternoon can exceed 35 degrees on a hot July day. This is actually great news for wine grapes, which thrive on warm days and cool nights. For visitors, it means morning activities are pleasant and afternoons call for shade or a cool dip in one of the town's famous hot spring pools. You can also read more about why September stays warm even as summer winds down, which matters for fall harvest visits.

Calistoga has the least fog of any major town in the North Bay, and it's not particularly close. The town averages just 1.3 fog hours per day across the full year. In summer, fog is essentially absent, with June through September averaging under 0.5 hours. Even in the foggier winter months, the valley geography means coastal marine layer rarely penetrates all the way to the northern end of Napa Valley. The low ridgelines that run east-west generally stop the fog bank well south of Calistoga, around the Carneros region or the southern end of the valley. On mornings when fog does appear, it tends to be thin and burns off by 9 AM. This is a dramatic contrast to towns like Petaluma or the Sonoma coast, which can sit fog-bound all morning. Nearby St. Helena also benefits from this northern valley shelter, but Calistoga arguably edges it out on fog-free days, partly because its elevation and position keep it just above the typical inversion layer. The reason this valley sees so little fog is exactly what Bay Area microclimates are built on: geography and distance from the ocean combine to create a completely different climate within 50 miles of the coast.

The morning-to-afternoon temperature swing in Calistoga demands layers, even in summer. Mornings start cool, typically 50-60°F from spring through fall, so a light jacket or long-sleeved layer is useful for early walks or patio breakfasts. By afternoon, you'll be stripping down to a t-shirt as temperatures climb into the 80s or 90s. In summer, bring lightweight, breathable clothing and strong sunscreen. The 9.6 daily hours of sunshine are relentless, and the valley position means you're not getting much sea breeze to cool you off. In winter, temperatures are mild compared to most of the US but still cool enough to want a real jacket: highs hover around 57-61°F and mornings dip into the 40s. Rain gear is essential from November through March. The key insight about dressing for Bay Area weather applies here with a twist: unlike San Francisco where layers handle fog and wind, in Calistoga they handle the daily heat cycle. Peel off layers as the day heats up, add them back as the sun goes down.

Calistoga receives about 38.3 inches of rain per year, which is higher than the Bay Area average but concentrated into a tight seasonal window. The town sees roughly 76 rainy days annually, almost all of them between November and April. In summer, months like June, July, and August average under half an inch of total precipitation, making the dry season genuinely dry. What distinguishes Calistoga from southern Napa Valley towns is that it sits at a slightly higher elevation and catches more moisture from winter storm systems that move in from the northwest. The rainiest months in the Bay Area are typically November and December, with storms delivering the bulk of the annual total in a few big events. The upside of this concentration is that summer visitors almost never see rain, while winter visitors get lush green hillsides and dramatic storm light. The 38 inches of annual rainfall is also what makes Napa Valley agriculture so productive without irrigation in dry years.

Yes, meaningfully so. Calistoga runs about 3-5 degrees warmer than St. Helena on summer afternoons. Both towns benefit from Napa Valley's fog shelter and inland position, but Calistoga sits at the northern end where the valley narrows and air circulation slows. Heat builds more efficiently there. St. Helena at 262 feet and Calistoga at 362 feet might seem similar, but the geographic context differs. Calistoga also gets slightly less cool air drainage from the hills on hot nights. In winter, the towns are essentially equivalent, both seeing highs around 57-61°F. Where Calistoga really distinguishes itself is during heat events: when the valley heats up, Calistoga consistently reads the highest temperatures. For hot springs visitors and those seeking maximum warmth, this matters. Angwin, sitting higher in the hills above the valley, is noticeably cooler and foggier than Calistoga, with more moderate summer temperatures but shorter, cloudier days.

Fall in Calistoga is one of the best seasons to visit, though it gets overshadowed by spring. September maintains warm temperatures around 85°F average high, with low rainfall and excellent sunshine. October cools to about 72°F and begins to see more cloud cover, but it remains comfortable and the valley takes on beautiful harvest colors. November marks the turn toward winter: temperatures drop to 60°F and rain becomes likely. The Bay Area's fall heat pattern is relevant here too. Indian summer heat waves are common in September and October, pushing Calistoga into the mid-90s during offshore wind events. These are warm, dry winds from the north and east that compress and heat as they descend into the valley. For wine country visitors, this heat completes grape ripening before harvest. For visitors, it means September can be hotter than you expect based on the calendar. The valley in fall also experiences some of its most dramatic weather contrasts: blazing afternoons followed by genuinely cold nights once the rains start, which can drop to 35-40°F in November.

Robert Louis Stevenson State Park sits on the slopes of Mount St. Helena above Calistoga, and the weather difference between the town and the peak is striking. Calistoga at 362 feet averages 73.6°F highs, but as you climb toward Mount St. Helena, temperatures drop roughly 3-5 degrees per thousand feet of elevation gain. The summit at over 4,300 feet can be 20-25 degrees cooler than Calistoga on summer days when the valley is baking. The mountain also intercepts moisture from Pacific storm systems, receiving more precipitation than the town below. In winter, snow occasionally dusts the upper slopes, though it's rare at Calistoga's elevation. Wind is also a factor on exposed ridgelines: while Calistoga proper is sheltered, the park's summit and upper trails get steady winds that don't reach town. If you're planning to hike up from Calistoga, bring an extra layer even in summer. The temperature at the trailhead and the temperature at the top can feel like two different seasons.

Calistoga's warmth comes from its position at the northern, sheltered end of Napa Valley, far from the Pacific coast and ringed by hills. The Bay Area's famous microclimates are driven by the ocean: coastal towns stay cool because marine air pours through gaps like the Golden Gate, while inland valleys heat dramatically once cut off from that maritime influence. Calistoga is roughly 50 miles from the coast, and the ridges separating it from the ocean are high enough to block the marine layer from ever reaching the northern valley. On a typical summer day when San Francisco is 62°F under fog, Calistoga is 92°F under clear sky. This is a 30-degree difference across 50 miles, which is exactly what Bay Area microclimates are famous for. The thermal dynamics also reinforce themselves: the valley heats rapidly, drawing cool air from the coast during afternoon hours, but that air warms as it travels inland. By the time any marine influence reaches Calistoga, it has been stripped of its cooling effect. Hot springs have flourished here for over a century precisely because of the geothermal heat and the reliably warm climate that makes outdoor soaking pleasant almost year-round.