Wintrovert

A personality type where one becomes quieter, more introverted, more withdrawn in the winter.

"She'd rather spend New Year's Eve at home, she's a wintrovert."

Wintrovert

Someone who develops extreme hermit-like, anti-social tendencies due to cold and or snow. Wintroverts tend to be social during nice weather so the prolonged shut-in behavior is seasonal more than typical.

Sarah: Hey, we should go grab a post-holiday cocktail soon.
Ken: I would but I become such a wintrovert this time of year. See ya in the spring.