Napa Valley Weather by Month: What to Pack and Expect
Napa Valley enjoys a Mediterranean climate with warm, dry summers (highs of 82-84°F) and mild, wet winters (highs of 57-63°F). Expect morning fog from June through September that burns off by mid-morning, and pack layers year-round since temperatures can swing 30-40 degrees between morning and afternoon.
Planning a trip to wine country? Understanding Napa Valley weather by month is essential for packing the right clothes and making the most of your visit. The region enjoys a Mediterranean climate with warm, dry summers and mild, wet winters, but conditions vary significantly depending on when you visit.
This guide breaks down what to expect each month, explains the famous morning fog phenomenon, and provides practical packing lists for every season. For comprehensive trip planning, see our complete Napa Valley travel guide and best time to visit guide.
Napa Valley's Mediterranean Climate
Napa Valley experiences approximately 260 sunny days per year (NOAA/National Weather Service), with temperatures ranging from 39 degrees Fahrenheit in winter to 84 degrees Fahrenheit in summer. Annual rainfall averages 20-27 inches (Western Regional Climate Center), falling almost entirely between November and March.
The valley's climate creates ideal wine-growing conditions. Warm, dry summers allow grapes to ripen fully, while cool marine influences and significant day-to-night temperature swings preserve balanced acidity.
Month-by-Month Weather Guide
Winter (December through February)
| Month | Avg High | Avg Low | Rainfall |
|---|---|---|---|
| December | 59 F | 40 F | 3.82 in |
| January | 59 F | 40 F | 4.17 in |
| February | 63 F | 42 F | 3.95 in |
Winter brings Napa's wettest weather, but the valley takes on serene beauty during this quiet season. Vineyards rest under dormant vines, and you will find uncrowded tasting rooms with intimate winemaker experiences. February brings the famous mustard bloom, when bright yellow flowers carpet the vineyards.
What to Expect: Reduced crowds, cozy tasting rooms, mustard blooms (late January through March), occasional frost at night, and mild daytime temperatures perfect for activities between rain showers.
Spring (March through May)
| Month | Avg High | Avg Low | Rainfall |
|---|---|---|---|
| March | 68 F | 44 F | 3.01 in |
| April | 72 F | 46 F | 1.26 in |
| May | 77 F | 50 F | 0.80 in |
Spring marks the transition to warmer, drier weather. March still sees regular rain, but by April rainfall drops significantly. Vineyards awaken with bud break, wildflowers bloom across hillsides, and the landscape turns lush green. This shoulder season offers excellent value and pleasant weather for outdoor tastings and cycling.
What to Expect: Comfortable temperatures, decreasing rain through the season, green hillsides, bud break in vineyards, and fewer crowds than peak season.
Summer (June through August)
| Month | Avg High | Avg Low | Rainfall |
|---|---|---|---|
| June | 82 F | 54 F | 0.22 in |
| July | 83 F | 56 F | 0.01 in |
| August | 84 F | 56 F | 0.02 in |
Summer brings warm, dry conditions with virtually no rainfall. Temperatures reach the low-to-mid 80s, occasionally climbing into the 90s. Morning fog is common during summer months, burning off by mid-morning to reveal sunny afternoons. Evening temperatures drop into the 50s, perfect for outdoor dining.
What to Expect: Hot afternoons, cool foggy mornings, consistently sunny skies, busy tasting rooms, and the beginning of early harvest for sparkling wine grapes in late August.
Fall and Harvest (September through November)
| Month | Avg High | Avg Low | Rainfall |
|---|---|---|---|
| September | 84 F | 53 F | 0.07 in |
| October | 78 F | 49 F | 0.93 in |
| November | 66 F | 44 F | 1.97 in |
Fall is the most exciting time in Napa Valley. Harvest season runs from late August through October, with vineyards buzzing as crews pick grapes and wineries process the new vintage. October offers arguably the best weather: comfortable mid-70s temperatures, minimal rain, and stunning fall colors transforming the vineyards.
What to Expect: Harvest activities, warm September days cooling through November, fall colors, the return of rain in late October, and peak visitor numbers during harvest.
Why Does Napa Valley Have Morning Fog?
One of Napa Valley's defining weather features is its famous morning fog. Cold Pacific currents chill marine air, creating fog that gets drawn through San Francisco Bay and up through the Mayacamas Mountains into the valley.
The fog acts as a natural air conditioner, cooling vineyards during hot summer days. This helps balance grape acidity and sugar levels, contributing to wine quality.
Fog is heaviest in southern Napa Valley near San Pablo Bay, while the upper valley near Calistoga sees less fog. On most summer days, fog burns off by 10 or 11 AM, revealing clear skies. Plan outdoor activities for late morning or afternoon when visiting during summer.
How Do Microclimates Vary Across Napa Valley?
Napa Valley spans just 30 miles north to south yet contains remarkable climate diversity across 16 American Viticultural Areas. This variation means weather conditions can differ dramatically depending on where you visit on any given day.
Temperature Variations: In southern Carneros, average summer highs reach 80 degrees Fahrenheit. Up-valley near Calistoga, temperatures can climb to 95 degrees Fahrenheit. Daily swings of 40 degrees are possible in some areas, making layers essential regardless of season.
Southern Valley (Carneros): Cooler temperatures, more fog, stronger marine influence. The fog can linger until noon during summer months, creating a mystical atmosphere but cooler morning temperatures. Ideal for Pinot Noir and Chardonnay due to the extended growing season.
Central Valley (Oakville, Rutherford): Moderate temperatures with good sun exposure and protection from both marine fog and extreme heat. The famous "Rutherford Dust" terroir produces some of Napa's most sought-after Cabernet Sauvignon. Expect temperatures 5-8 degrees warmer than Carneros.
Northern Valley (Calistoga, St. Helena): Warmest temperatures, less fog, fuller-bodied wine styles. Hot summer afternoons can reach the mid-90s, so plan visits here for morning or late afternoon when temperatures are more comfortable.
Mountain Vineyards (Howell Mountain, Spring Mountain, Diamond Mountain): Above 1,600 feet, vineyards sit above the fog line, receiving more sunshine despite cooler overall temperatures. Mountain sites experience less temperature variation than valley floor locations and offer stunning views on clear days.
Practical Planning Tip: If you are visiting multiple AVAs in one day, start in the cooler southern valley and work your way north as temperatures rise. This approach keeps you comfortable throughout the day.
How Weather Affects Wine Quality
Napa Valley's weather patterns directly influence the wines you taste during your visit. Understanding this connection adds depth to your tasting room experiences.
As legendary winemaker Robert Mondavi once observed, "Wine is sunlight, held together by water." This poetic description captures how weather shapes every vintage.
Warm Days, Cool Nights: The 30-40 degree temperature swing between day and night is critical for quality winemaking. Hot days build sugar and flavor compounds in grapes, while cool nights preserve acidity and freshness. This balance creates wines with both richness and elegance.
Morning Fog: Beyond its photogenic qualities, morning fog slows grape ripening, extending the growing season. Longer hang time allows grapes to develop complex flavors while maintaining acidity. Wines from foggy southern Napa often show more finesse and lighter body.
Drought vs. Rain Years: In drought years, vines produce smaller berries with more concentrated flavors and thicker skins, resulting in intense, tannic wines. Wetter vintages produce larger berries with softer tannins and more approachable wines in their youth.
Heat Spikes: Occasional heat waves (temperatures above 100 degrees Fahrenheit) can stress vines and accelerate ripening. Skilled winemakers adjust harvest timing and vineyard management to mitigate these effects.
Seasonal Packing Lists
Spring (March through May)
Clothing:
- Light layers: long-sleeve cotton shirts, light merino sweaters, and breathable blouses
- Comfortable walking shoes with good traction (gravel paths are common at wineries)
- Light jacket or fleece for cool mornings and air-conditioned tasting rooms
- Waterproof rain jacket with hood for early spring showers
- Smart-casual attire for tasting rooms (nice jeans, khakis, or casual dresses)
- Sunglasses and a packable sun hat
Essentials:
- Compact travel umbrella (essential in March and April)
- Sunscreen SPF 30+ (UV can be strong even on cloudy days)
- Reusable water bottle
- Light scarf (versatile for warmth and style)
Summer (June through August)
Clothing:
- Breathable, lightweight fabrics: linen shirts, cotton blouses, moisture-wicking materials
- Comfortable sandals for casual settings and walking shoes for winery tours
- Light cardigan or pashmina for foggy mornings and overly air-conditioned tasting rooms
- Wide-brimmed hat for sun protection during outdoor tastings
- Smart-casual evening attire for dinner reservations (temperatures drop to pleasant 50s)
- Sunglasses with good UV protection
Essentials:
- High SPF sunscreen (SPF 50+ recommended)
- Reusable water bottle (hydration is essential; aim for 8+ glasses daily)
- Cooling towel or portable fan for hot afternoons
- Lip balm with SPF
- After-sun lotion for extended outdoor time
Fall (September through November)
Clothing:
- Versatile layers: t-shirts, long-sleeve shirts, light sweaters, and a medium-weight jacket
- Packable waterproof layer for late fall rain
- Comfortable closed-toe walking shoes (harvest activity means muddy vineyard paths)
- Warm scarf and light gloves for November evenings (temperatures can drop to low 40s)
- Earth tones and warm colors photograph beautifully against fall foliage
Essentials:
- Compact umbrella (especially November)
- Sunscreen (UV remains strong through October)
- Camera or phone with good camera for fall colors
- Hand lotion (dry air can be tough on skin)
Winter (December through February)
Clothing:
- Warm layers: wool sweaters, fleece, and a packable light down jacket
- Quality waterproof jacket with hood
- Comfortable waterproof boots or shoes with non-slip soles
- Warm scarf, hat, and gloves for early morning fog and cool evenings
- Smart-casual indoor attire for cozy tasting room experiences
- Extra socks (wet feet can ruin a wine tasting day)
Essentials:
- Quality compact umbrella (wind-resistant recommended)
- Waterproof bag or pouch for electronics
- Hand warmers for particularly cold mornings
- Moisturizer (indoor heating plus rain creates dry skin)
- Waterproof phone case for vineyard photos in drizzle
Weather-Proof Your Trip
Regardless of when you visit, staying in a well-appointed luxury vacation rental ensures comfort in any weather. Properties with amenities like heated pools, hot tubs, fire pits, and spacious indoor living areas let you enjoy wine country regardless of conditions. On rainy days, a gourmet kitchen becomes the perfect place to prepare local ingredients, while a hot tub under the stars makes cool evenings magical.
Frequently Asked Questions
What is the best month to visit Napa Valley for weather?
October offers warm days (mid-70s), minimal rain, and harvest season atmosphere. September is equally beautiful with slightly warmer temperatures. For fewer crowds with good weather, consider April and May.
Does it rain a lot in Napa Valley?
Napa receives 20-27 inches of rain annually, almost entirely between November and March. Summer months are virtually rainless, with July and August averaging less than 0.05 inches.
How cold does Napa Valley get in winter?
Winter nights dip to the upper 30s or low 40s, with occasional frost. Daytime highs reach the upper 50s to low 60s. Snow is extremely rare in the valley.
Is morning fog a problem for wine tasting?
Morning fog typically burns off by mid-morning, rarely affecting wine tasting activities. Many visitors find the fog adds atmosphere. Schedule outdoor activities for late morning or afternoon if clear views are important.
What should I wear to wine tastings?
Smart-casual attire works everywhere: nice jeans or slacks, comfortable but polished shoes, and layered tops. Avoid flip-flops and athletic wear at higher-end establishments. Always bring a layer for air-conditioned spaces.
How much does temperature vary across Napa Valley?
On summer days, southern Carneros reaches 80 degrees Fahrenheit while Calistoga in the north hits 95 degrees Fahrenheit. This 15-degree difference is significant, so check forecasts for your specific destinations.
When is harvest season?
Harvest runs from late August through October, with peak activity in September. Sparkling wine grapes are picked first, followed by whites and then reds. Exact timing varies by vintage.
