When I was a child I thought of September as the yellow month. I grew up by the coast and the autumn colours are not as vivid there as they can be other places. The leaves go yellow and then quite rapidly brown. That is if they are lucky enough to stay on the trees long enough to turn brown before being swept away by the wind.
I like September better than August. Now I can settle into autumn because I know that summer is definitely over. Often September surprises with warm days and lots of sunshine. Like now!