Living in Northern California, in the Bay Area the weather is pretty mild. The winters aren't terribly cold and it doesn't snow. It does rain, but even that's been light of late. Looking at my knitted wardrobe it mostly consists of accessories like scarves, shawlettes and socks. I have a few large shawls and stoles and even fewer sweaters. The rest of the items seems to consist largely of vests and shrugs, they are the perfect thing for Spring or Fall around here and a wonderful vehicle for all sorts of yarns in various weights and content.
I like knitting with wool the best. It's easiest on my hands and therefore more comfortable and enjoyable to knit. I tend to gravitate more now to the dk weights and I love the new trend for knitting sock weights at a worsted gauge. I don't knit as much during the summer because working with the wool tends to make me and my hands more hot and sticky. I suppose my cotton/linen projects are more appropriate on the more hot and humid days, but I don't have as many of those and wool dominates the stash. The rest of the year I'm probably knitting the same sort of things with the same sorts of yarns.
So I don't consider myself a seasonal knitter, rather a constant knitter with summer (and just the hottest days at that) only a short respite from knitting.