Redwoods are generally well behaved compared to other trees and their behavior is consistent throughout the year.
Does that help?
Steve
Actually those naughty redwoods have been known drop branches on people when the wind comes up strong. I was walking under them with a 4x5 during a 60+mph wind storm. Never set the camera up...I was too busy looking out for branches falling from 150 feet or more above me! But it was a great experience! Occasionally one comes across strange 'trees" sticking in the ground -- 6 to 10 inches in diameter at the base, but they get wider at their tops. Widow-makers is one name for them...
But really, any time of the year can be good. If there is a less desirerable time it would be the summer months (too much sun and usually a bit of a breeze). I like late Fall and Winter the best...late Fall for the little bit of Fall color (usually yellow) of the Big Leaf Maples and the berries...a yellow filter really pops these in B&W. Winter when the leaves have fallen, the views through the redwoods open up...especially along the creeks.
May has the rhododendrons blooming and a good amount of water in the creeks and rivers. The redwoods on the flood plains of the Eel River in the southern part of the county are more open and good to work in. I prefer the redwoods of the northern county - especially along the creeks. The forest vegetation tends to be a bit thicker, but there are still much to photograph. Also there is no poison oak in the north and as I often go off-trail, it is nice not to have to worry about it.
The number of windless days are less in May, so that might limit long exposures -- but that is something one always has to work with in the dense forest. Most photographers would want to work on overcast/foggy days to reduce the contrast (still plenty, though!). May would have some days like this. But with this dang global warming, we seem to get less fog than we use to.
But this is the advantage of living here -- one can pick the weather conditions and head out when things seem to line up right. And once in the redwoods, if the weather turns too windy, or too sunny or too much rain, well, one just enjoys being there, knowing one can come back another day.
Any particular type of images you want to make, Keith? (color, B&W, etc.). The coast is pretty nice, too.
Vaughn