Yup! And it depends on the cat, too. I knew an indoor-only longhaired cat who not only grew in a winter coat, his black fur got lighter in the winter, too. (It looked like he suddenly became much older, with lots of grey and white fur mixed in with the black and brown.) My own (indoor-only) cats definitely have a great big shedding and regrowth period about this time of year (Spike looks distinctly shaggy, as a result), and there'll be another one to follow it in spring.