Can typically be identified thanks to the attire's characteristics: a red outfit with a green skirt resembling a christmas tree, a green ribbon along the center of her torso depicting a golden star, a golden tiara adorned with stars, two red detached sleeves with fur trim on her forearms, and a red choker with a christmas wreath shaped clasp.
Note that it's possible (especially for older artwork), to depict Sothis in a winter outfit without it being the one described above, in which case this tag should not be used.