Continued from: Redwoods - Prolific Producers
In the Age of the Dinosaurs, redwood species were dominant over much of the Northern Hemisphere, including what is now the Arctic. The climate was then humid and mild over a much larger region than today. Over millennia climate change reduced redwood habitat.
The abundant moisture and moderate temperatures of coastal northern California and extreme southern Oregon allow the redwood to flourish. This ocean-moderated climate is very humid; average yearly rainfall measures between 63 and 310 centimeters (25 to 122 inches). But annual precipitation seems less important than the frequent summer fog.
The passage of warm, moist marine air over the cold surface waters of the Pacific creates fog here almost daily in summer. It frequently lasts until afternoon, when it burns off. Another fog bank may move in before sunset.
The fog decreases the trees' loss of water through evaporation and transpiration and adds moisture to the soil. So the coast redwood is generally restricted to this coastal fog belt. Continued.