In general, girls get cold way easier than guys do. My hands are naturally warm so a little trick I use sometimes when I see them shivering is to say "Hey, let me see how cold your hands are" and lightly grab their hands. Without fail, they'll go absolutely nuts over how warm my hands are in comparison and start clinging onto them for dear life. Found it works very well with shy girls too since their aversion to the cold overrides all other thought processes. Effortless kino. Plus you can tease them about how easily they get cold or how touchy feely they're getting.