Early autumn · Weather & things to do
Sonoma in September
Sonoma edges cooler than August, with highs of 88°F (31°C), lows of 57°F (14°C) and about 0.1 in (3 mm) of rain.
It scores 83/100 for comfort, 7th of 12, which makes it a solid shoulder-season month.
- Avg high
- 88°F (31°C)
- Avg low
- 57°F (14°C)
- Rain
- 0.1 in (3 mm)
- Humidity
- 47%
- Cloud cover
- 21%
- Daylight
- ~12 h 14 min
- Comfort score
- 83/100 · Great
What September feels like
Heat sets the pace, with highs around 88°F (31°C). Get out early and keep the hottest hours for somewhere cool.
Mornings start much cooler: lows average 57°F (14°C), about 17°C (31°F) below the afternoon high.
Rain is scarce: about 0.1 in (3 mm) for the whole month.
Sunny spells dominate: cloud cover averages 21%.
Plan around September
September is shoulder season: good weather, a step below the best months (April – June and October & November).
- Comfort improves from 76/100 in August to 83/100.
- September sits inside the Apr – Oct window our California Wine Country route recommends.
What to pack for September
- Light, breathable clothes88°F afternoons
- Sunscreen, sunglasses and a hatstrong sun this month
- Refillable water bottleeasy to dehydrate in the heat
- A warm layer for eveningsnights drop to 57°F
- Comfortable walking shoesmost places below are best reached on foot or with short walks
What to do in Sonoma in September
Afternoons run hot (88°F), so these picks mix early-start outdoor spots with cool indoor breaks.
Mission San Francisco Solano
The last of California's 21 missions, part of Sonoma State Historic Park.
Why now September scores 83/100 for comfort, good conditions for being outside.
Basque Boulangerie Café
Plaza bakery for pastries, coffee and sandwiches to take on the road.
Why now Highs near 88°F and 0.1 in of monthly rain make this an easy outdoor pick.
Gundlach Bundschu Winery
Family winery since 1858, with hillside vineyards and a relaxed tasting room.
Why now A break from 88°F afternoons.
Sonoma Plaza
California's largest town square, ringed by tasting rooms and shops.
Why now One to do outside while the weather is on your side.
Glen Ellen Star
Small wood-fired kitchen serving pizzas, roasted vegetables and local wines.
Why now Somewhere to sit out the hottest hours.
Nearby in September
- Napa in September~18 mi · highs 85°F, 0.1 in rain · 2°C (3°F) cooler by day, about as wet
- Healdsburg in September~31 mi · highs 76°F, 0.2 in rain · 7°C (12°F) cooler by day, about as wet
- San Francisco in September~36 mi · highs 74°F, 0.2 in rain · 8°C (14°F) cooler by day, about as wet
- Old Sacramento Waterfront in September~55 mi · highs 91°F, 0.2 in rain · 2°C (3°F) warmer by day, about as wet
NASA POWER 2001–2025 monthly averages on a ~50 km grid, temperatures adjusted from the grid cell's ~266 m to Sonoma's ~26 m elevation (standard lapse rate). Comfort scores weigh temperature, rain, humidity and cloud: see how we score each month. Check a forecast before you go.
Sonoma in September: quick answers
Is September a good time to visit Sonoma?
It's a good shoulder-season choice, scoring 83/100 against a best of 100 in April – June and October & November. Expect highs of 88°F (31°C) and 0.1 in (3 mm) of rain. September is inside the Apr – Oct window our California Wine Country route recommends.
How hot is Sonoma in September?
Average highs are 88°F (31°C) and average lows 57°F (14°C), making it the 3rd-warmest month by daytime highs.
Does it rain a lot in Sonoma in September?
Not much: about 0.1 in (3 mm) of rain falls across September on average, the 3rd-driest month of the year. The annual total is about 27.1 in (689 mm).
What should I pack for Sonoma in September?
Bring light, breathable clothes (88°F afternoons), sunscreen, sunglasses and a hat (strong sun this month), refillable water bottle (easy to dehydrate in the heat), a warm layer for evenings (nights drop to 57°F) and comfortable walking shoes (most places below are best reached on foot or with short walks).
Routes in season in September
- California Wine Country Apr – Oct
Planning Sonoma in September?
Plan it together in TripsCircle: one itinerary, one shared packing list and costs split as you go.