Rats are hardy about many things but not about cold, drafty air. Their airways are their weak point all year, and winter in a heated house gives them the worst combination: dry air from radiators, cold drafts at cage level, and temperature swings between warm evenings and cold nights. A rat kept in a steady room, with deep nesting to burrow into alongside his cagemates and his basics checked daily, usually sails through winter. A rat in a cage by a window in a spare room may spend the season sneezing, hunched, and quietly losing condition.
Choosing the winter spot for the cage
Keep the cage in a room the household actually heats and uses, holding roughly sixty-five to seventy-five degrees as steadily as you can manage. Keep it off the floor, away from single-glazed windows and doors that open to the outside, and not pressed against a radiator. A spare room that is warm when guests visit and cold the rest of the week is a poor winter home even if it is peaceful. Cagemates are part of the heating system, since rats sleep in a shared pile and warm each other, so a rat housed alone needs noticeably more nesting material and a closer eye on room temperature.
Nesting, hammocks, and houses that hold warmth
Give the group far more nesting than you offer in summer: unscented paper bedding to tunnel in, plain paper strips and tissues to carry, and a house or enclosed hide they can pack until only a small entrance remains. Fleece hammocks, ideally double-layered or in a pocket style they can climb inside, become winter sleeping spots rather than the thin cotton of summer, and a spare hammock rotation lets you wash one set without stripping their warm bed. Spot-clean wet corners daily but leave the main nest largely intact between deeper cleans, because rebuilding insulation nightly in a cool room costs a rat energy he should spend on staying well.
Eating, drinking, and keeping condition
Rats staying warm and active burn a little more, so keep their usual food freely available and expect appetites to rise slightly rather than rationing to a summer measure. The critical check is water: bottle balls stiffen and stick more in cold rooms, and a group can go quietly short if the one bottle fails. Press the tip daily to confirm flow, consider a second bottle in winter as insurance, and refill with room-temperature water. Handle each rat weekly, feeling ribs and spine under the fur and noting weights if you can, because a winter coat of fluff hides weight loss well until it is advanced, especially in an elderly rat.
Airway health in heated houses
Listen to your rat's chest-side sounds as part of winter handling. Occasional sneezes in new bedding are common, but persistent sneezing, a wheeze or click when breathing, red discharge around the eyes or nose, a hunched, puffed posture, or one rat repeatedly leaving the warm pile to sit alone all warrant a veterinarian, sooner for an older rat. Keep bedding low-dust and unscented, open a window briefly for fresh air without drafting the cage, and never use scented candles or sprays near the cage to make a winter room smell nice; a rat breathes that air at close quarters all day.
Noticing changes when several people help
A rat's early winter decline is subtle: slightly less food taken, a little less interest in coming out, a softer body under the fluff. Those details get lost when different family members feed and clean on different days with nothing written down. Recording appetite notes, weights, and any sneezing in your rat's shared profile through KinsLe Family Sharing means the whole family is looking at the same picture of his winter health, not each holding one evening's impression.