The climate of the Mendenhall Valley is that of a temperate rainforest, influenced by coastal weather patterns and microclimatic fluctuations. Precipitation is high, sunshine is scarce, and temperatures tend to be moderate, averaging 30 degrees in winter and 55 degrees in the summer. The average length of the growing season in Juneau is 146 days. Mean annual precipitation averages 54.56 inches. There are four successional vegetative stages in the Mendenhall Valley.
Standard vegetation is a hemlock-spruce forest.
Successional stages leading up to forest growth are initially pioneering on exposed bedrock by the lichen Placopsis gelida , followed by Rhizocarpon geographicum . Second stage growth is characterized by herb growth, and third stage growth is a shrub phase of alders, willow, and small cottonwoods. Location was determined using GPS and the Juneau B-2 quadrangle map. Elevation data was determined primarily by correlation with map contours after determining site location. Moraine dates were taken from dendrochronologic measurements published on R.D.Miller s Surficial Geologic Map of the Juneau Urban Area and Vicinity, circa 1975.