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Muir Woods Weather: The Micro-Climate of the Redwood Forest
Muir Woods is located in a narrow valley over 1,000 feet (300 Meters) above San Francisco Bay, and just across a ridge from the Pacific Ocean. The ocean fog plays a critical role in the health of the old-growth redwood forest, providing moisture to the redwoods during the dry summers of Northern California.
Unlike many trees, the redwoods can absorb moisture directly from the fog without it falling as rain. This has only really been documented thoroughly in the last 30 years. You can read a layman’s article about this process and the possible impact of global warming, and you biology buffs can find a scientific article here about foliar water uptake.
Temperatures here at Muir Woods rarely exceed the low 70’s F (the low 20’s in degrees C.) on all but the very hottest days of the year, and fog makes an appearance most days in both the morning and the late afternoon.
Insiders Tip: Even if it’s a hot summer day down the hill in Mill Valley and Sausalito, be sure to bring a sweater or windbreaker for your visit to Muir Woods. On warm days there can still be a chilly breeze and the valley floor is shadowed by the large trees and nearby slopes. On cool winter days we advise bringing a good coat or jacket. More details are below.
What Time of Year was Vertigo Filmed in Muir Woods?
Insiders Tip: You may have seen the atmospheric Muir Woods sequence from the famous suspense film Vertigo (1958) with Kim Novak and James Stewart in the video below. Director Alfred Hitchcock used filters to darken the setting for dramatic effect to mirror the mood of the scene. Your actual visit to a redwood forest, even on a cloudy day, will be brighter than this!
The secret of the Muir Woods scene from Vertigo? It wasn’t shot in Muir Woods, though its true location was one that deliberately mirrors the Muir Woods experience!
Muir Woods from May through August
Summers in the San Francisco Bay Area are dry, with rain a rarity from June through August. Muir Woods weather can be very different from “down by the Bay,” buts its rainfall follows these same rules.
Ironically, though, summers here are the high season for fog, which is just what the redwoods are looking for. The marine layer invades the Bay each afternoon to settle in for the night. The fog retreats from the mid-day heat to hover along the coast, then re-enters the Bay mid-afternoon to repeat the process.
If you visit Muir Woods from May through August, assume there will be fog each morning and afternoon and dress warmly. Once in a while the fog will stay away, but even then the shady trails are subject to cool breezes from the Pacific.
Muir Woods from September through October
The local climate in early autumn remains very much like summer, but the fog often recedes and we can have some of our warmest days of the year. For this reason many people will find September and October to be the nicest time of the year to visit, with Muir Woods weather warm and sunny Woods.
This is also the time of the year when we (in non-drought years!) get our first significant rains of the season, although they are often followed by weeks of sunny days.
Some afternoons in the fall we’ll have strong winds blow across the ridgetops, usually coming off the Pacific Ocean. Although the wind will be weaker down in the valley and the redwoods themselves help slow down the flowing air, some afternoons can feel quite chilly in the breeze.
Muir Woods from November through April
The rainy season in the San Francisco Bay Area and Marin County features cold, wet Pacific Ocean storms that blow in from the northwest. Between the storms we can have crisp, clear, beautiful days in Muir Woods with temperatures in the 40’s and 50’s F (5 to 15 degrees Celsius).
Visiting the Park this time of year calls for a warm jacket and an umbrella or a good raincoat. Muir Woods weather in the winter brings even more rain than down at sea level. If you come on a sunny day, just remember that Muir Woods closes at sunset and that the mornings can be the most glorious time to see the redwood groves in all their splendor.
On a personal note, I think there are few more special places and times on earth than being in Muir Woods early in the morning after it rained the night before. The smell and the feel of the air cannot be described, they just have to be felt — all I can say is that the sense of cool peace wraps me up and puts me in a very soothing and thoughtful place.