I've always worked to the Met Office definition of the seasons (even when I was a child, well before I ever realised that my thinking actually tied in with that of the meteorologists):
Winter: Dec/Jan/Feb
Spring: Mar/Apr/May
Summer: Jun/Jul/Aug
Autumn: Sep/Oct/Nov
Anyway, one look at the leaves on the trees around you (with their beautiful colours) should tell you that it's still autumn. It's not winter until the branches are bare!