A healthy adult rabbit is built for cold far better than for heat, wearing a dense winter coat and coping happily at temperatures that would chill many pets. Winter trouble for an indoor rabbit usually comes from the house, not the weather: radiators drying and overheating one corner, drafts at floor level where he lives, shorter days quietly shrinking his exercise time, and owners changing his routine. Keep his temperature steady, his hay unlimited, his water liquid, and his days active, and most rabbits come through winter in excellent condition.
Steady and cool beats warm and swinging
Keep your rabbit's room at a fairly even, moderate temperature and position his pen away from both radiators and outside doors. A rabbit moved between a hot evening room and a cold night room, or brought indoors suddenly from a cold hutch mid-winter, can struggle with the abrupt change and even begin to lose his winter coat at the wrong time. Floor level is his world, so check for drafts where he actually sits by sitting there yourself. If he has always lived outdoors, any move inside for winter should be planned and gradual in feel, not a same-day plunge from frost into central heating.
Hay as food, bedding, and occupation
Hay does three winter jobs at once: it keeps his gut moving, wears his teeth, and gives him material to burrow into and rearrange. Fill his sleeping box deeply with clean, sweet-smelling hay and refresh it often enough that it stays dry, because damp bedding makes him colder rather than warmer and can irritate his feet and airways. Add a sturdy cardboard hide or box he can sit inside out of any draft, and expect to replace it as he shreds it. A rabbit eating less hay in winter deserves attention in his own right, since reduced hay intake shows up later as dental and digestive problems rather than an obvious cold-related illness.
Water, weight, and winter appetites
Check his water at least twice a day in cold weather, even indoors, because bottles can drip, stick, or chill near an exterior wall, and many rabbits drink more reliably from a heavy bowl that cannot tip. Cold weather and lower activity can quietly change his weight in either direction: an inactive rabbit may gain on the same pellets, while an older rabbit may lose condition. Feel over his ribs and spine weekly with your hands rather than judging by his fluffy outline, keep pellets measured rather than generously topped up, and weigh him if you can so a slow drift is caught while it is still easy to correct.
Keeping him moving on dark days
The most common winter harm is inactivity. Short evenings tempt everyone to skip the run-around time, yet hours shut in a pen leave a rabbit stiff, bored, and prone to sore hocks and weight gain. Protect a daily exercise period in a rabbit-proofed room or secure run, scatter some of his greens so he forages rather than eating from a bowl in one spot, and rotate simple toys and tunnels. Watch for him sitting hunched for long periods, moving reluctantly, or developing sore, reddened hocks, and raise those with a veterinarian rather than assuming winter laziness, especially in an older rabbit whose joints may ache in the cold.
One routine the whole house can follow
Winter care drifts when one person assumes another topped up the hay or checked the bowl on a dark evening. In the room where he burrows into deep hay, KinsLe Family Sharing gives relatives you select access to his profile.