Cold rarely kills an indoor cat. Space heaters, unvented gas and dehydration do. A cat will sleep 30 cm from a glowing element until the skin is damaged, and will drink less as the house dries out. Fix the heat sources, the water and the old cat's sleeping spot, in that order.
Space heaters: the 30 cm problem
Cats seek radiant heat and do not move when it starts to hurt. Contact burns appear on the tail tip, ear edges, nose and paw pads, often as a thickened, hairless, sometimes darkened patch the cat ignores for days. Keep any element at least 1 m from a bed or cat tree, fit a guard, and buy only models that cut out on tip-over. Oil-filled radiator heaters are safer than exposed halogen bars because the surface stays near 60°C rather than 300°C or more.
Never leave a heater running in an unattended room a cat can enter. A cat that chews cables risks oral burns and electrocution; run cords through conduit and switch off at the wall, not at the unit.
Carbon monoxide, the invisible one
Unvented gas, kerosene and propane heaters produce carbon monoxide. Early signs in cats — lethargy, vomiting, weakness, a wobbly walk — look like an ordinary off day, and gum colour is an unreliable clue. If two cats in one room are dull at the same time, suspect the air rather than the cats: open windows, shut off the appliance, move everyone out, and call the vet.
Fit a CO alarm within 3 m of every sleeping area and on every floor, test it monthly, and never run a barbecue, generator or camping stove indoors or in a garage attached to the house. A cat that recovers after fresh air still needs an exam, because CO binds haemoglobin and delayed neurological signs occur.
An outdoor shelter that actually works
- Raise the floor 10 to 15 cm off the ground on a pallet or foam board; ground contact is the largest heat loss.
- Turn the door away from the prevailing wind, opening 15 to 20 cm, with a flap the cat can push.
- Use straw, not blankets: fabric absorbs moisture and freezes, straw traps air and drains.
- Fill two thirds of the box with straw so the cat can burrow, not just lie on top.
- Cut two exits so a cat cannot be cornered by another animal.
- Insulate with foam board lined with straw; a 40 to 50 cm cube suits one cat, larger needs body heat to fill.
- Site it against a wall, under an overhang, off the ground and out of the wind.
A shelter that is too large is worse than one that is snug, because the cat's own heat cannot warm the air space.
How cold is too cold
Most healthy adults cope outdoors to about 7°C with a dry, raised shelter, and start to struggle below 0°C. Frostbite targets the ear tips, tail and paw pads, mostly at -10°C and below. Shivering, tight curling and refusing food are early hypothermia signs; severe cases go stiff, slow and unresponsive, and that is a same-hour emergency.
Very young, very old, thin and arthritic cats lose heat faster and should be indoors below 7°C. A cat that is wet in wind chill is in trouble far above freezing.
Senior cats lose heat faster
Normal rectal temperature is 38.1 to 39.2°C. Under 37.2°C is not "a cold cat", it is an emergency: the body is losing heat faster than it produces it, and the causes include sepsis, kidney disease and hypothyroidism. Old cats carry less muscle, thinner fat and arthritis that stops them walking to a warm spot.
Add a covered heated pad on the low setting, a draught-free bed at floor level rather than a high perch, and a 2 cm foam mat so the joints are not on cold tile. Check the pad for chew damage weekly; a chewed cable is a burn risk. More on senior cat care.
Paw pads, litter dust and dry air
Cracked pads in winter come from three things at once: indoor humidity under 30 percent, clay litter dust, and cold floors. Keep humidity at 40 to 50 percent, switch a cracked-pad cat to a low-dust or pellet litter, and use a pet-safe paw balm at night. Never use human hand cream: it softens the pad and the cat licks it off, and some formulations contain irritants.
Deep cracks that bleed, a cat that limps, or any pad with a black or swollen area needs a vet visit rather than a balm. Road salt and de-icer are irritants and are toxic if licked; wipe paws with a damp cloth after outdoor access and use pet-safe grit at home.
Less drinking, more urinary risk
Cats drink less in cold weather, and a dry-fed cat can drop below the 40 to 60 ml per kg per day it needs. Concentrated urine plus a winter of inactivity is the classic setup for cystitis and, in male cats, urethral obstruction. Use a fountain, place 2 to 3 water bowls away from the food, offer slightly warmed water, and add 1 to 2 tablespoons of water to each wet meal.
Straining in the box with little or no urine, yowling, hiding or repeated groin licking in a male cat is a same-hour emergency: a blocked cat can die within 24 to 36 hours. Read urinary blockage signs before you need them, and see how much water a cat needs.
Five steps for the first cold snap
- Move every heater at least 1 m from cat beds and fit a tip-over cut-out.
- Test the CO alarm and add one on the floor with the boiler.
- Set a heated pad on low with a cover, and put a foam mat under the old cat's bed.
- Add a fountain and two extra bowls, and warm the wet food slightly.
- Weigh the cat monthly; a 300 g loss in winter is a vet visit, not the cold.
Frequently asked
Is it safe to leave a space heater on for my cat all day?
Only an oil-filled radiator type with a tip-over cut-out, at least 1 m from any bedding, in a room you can inspect. Exposed halogen or fan elements reach 300°C and cause contact burns on tails and ears within seconds of prolonged contact. If you cannot check the room, use a heated pad with a chew-resistant cord instead.
What temperature is too cold for a cat indoors?
Below about 16°C most cats start seeking heat, and below 10°C an old, thin or arthritic cat is at real risk. Indoor cold matters most when the floor is cold, because cats lose heat through the pads and belly. Keep one draught-free warm bed at floor level and check that the cat is using it.
My cat's rectal temperature is 37.0 C. Should I wait?
No. Normal is 38.1 to 39.2°C, and anything under 37.2°C means the body is losing heat faster than it produces it. Warm the cat gradually with blankets and a warm room, never a hot water bottle against bare skin, and call the vet the same hour. Hypothermia at that level can accompany sepsis or kidney disease.