I am looking to permanently move my adult Russian tortoise to a new outdoor enclosure in Brooklyn, New York, where the average coldest winter temperatures are 25º Fahrenheit in February, with snow. As I prepare to construct his new outdoor enclosure, is there any feature or method I should keep in mind in order to set him up for success living outside year round under such conditions? I am looking for classic or creative solutions that don't involve any artificial or active intervention such as heat lamps, brumation in fridges, etc. Thank you!