If its a girl you could call her Summer to be ironic? haha
Loads of good ones listed there. I like colour names like Violet, Jade, and Ruby, they're quite dark so could maybe be wintery? Amber and Willow are autumny and two of my favourites.
I can't think of a single boys name except maybe Christian and Noel, although I don't particularly like Noel as I just think of Deal or No Deal.
Maybe if you had a book or film that you associated with winter you could pull a name from that?