Mill Valley in September
Great time to visit
September delivers arguably the year's best weather with summer warmth but fewer crowds. locals call it the secret season - warm days, clear skies, and more reasonable prices.
Weather
September often brings Mill Valley's finest weather - warm days in the upper 70s, comfortable nights around 55°F, and crystal-clear skies as the marine layer retreats. The dry season continues with virtually no rain.
26°C high13°C low1 rain days
Crowds & Cost
high crowds
~$250/day average
Events & Festivals
- •Mill Valley Fall Arts Festival
- •Harvest festivals at local wineries
- •Back-to-school hiking group meetups
September Tips
- •September has the clearest mountain views of the year - bring your camera
- •Restaurant patios stay busy late into the evening with warm weather
- •This is prime hiking season with lower crowds than summer
All Months
April through October gives you the best weather in Mill Valley. Summer means no rain but also means fog that rolls in most afternoons — pack layers even in July. May and September hit the sweet spot with warm days and clear skies. The Mill Valley Film Festival happens in October, bringing crowds and higher hotel rates. Winter brings rain that can last for days, but also fewer tourists and green hills that photographers love. Spring wildflowers bloom best in March and April along the Dipsea Trail. Avoid Memorial Day and Labor Day weekends unless you enjoy fighting for parking spots.
Mill Valley Scores
Solo
6/10
Couples
7/10
Families
8/10
Adventure
6/10
Budget
4/10
Luxury
6/10
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