Winter is the deadliest season for outdoor cats, and the difference between a colony that makes it through and one that doesn't usually comes down to a handful of concrete interventions — not luck.
Build a proper winter shelter — the specific design matters. A large plastic storage bin, 18 to 30 gallons, works far better than a wooden doghouse because plastic doesn't absorb moisture. Cut a single entrance hole about 6 inches across, positioned roughly 2 inches up from the base (raising it slightly keeps drafts and flood water out) and facing away from the prevailing wind. For real insulation, nest a smaller bin inside a larger one and pack the gap between them with rigid foam board or crumpled newspaper. Fill the interior with straw — not hay, and definitely not blankets or towels. Straw has hollow stalks that trap air and stay dry; fabric absorbs body moisture and ambient dampness, then goes cold and actually pulls heat away from the cat sleeping on it. Elevate the whole shelter a couple of inches off the ground on a wood pallet or bricks, and hang a flap of heavy fabric or a cut piece of pool-liner vinyl over the entrance to cut wind further.
Check under your car hood before starting the engine — every single cold day. Cats seek out warm engine bays, wheel wells, and the space above a still-warm exhaust system as reliable heat sources in freezing weather. A firm bang on the hood, a horn honk, or a quick visual check underneath takes five seconds and prevents one of the most common and gruesome winter injuries to outdoor cats. Make this an automatic habit from the first cold snap through spring, not just on days you happen to remember.
Keep water accessible and unfrozen. Dehydration, not hunger, is often the bigger winter threat, because cats will avoid drinking from ice and can become dangerously dehydrated in cold, dry air. Heated water bowls (solar-powered or plug-in versions exist for outdoor use) are the most reliable fix; if that's not feasible, swap out water at least twice a day. A deep, narrow bowl freezes slower than a wide shallow one, and placing the bowl inside a foam cooler with a hole cut for access adds meaningful insulation.
Increase food portions as temperatures drop. Outdoor cats burn substantially more calories maintaining body heat in cold weather — bump portions 25-50% above summer amounts during the coldest months. Wet food is nutritionally ideal but freezes fast outdoors, so put it out in small portions timed to feeding visits rather than leaving a full bowl sitting in the cold for hours.
Watch for antifreeze exposure. Ethylene glycol, the base of most traditional antifreeze, has a sweet taste cats find appealing, and even a teaspoon can be fatal. Clean any driveway or garage spills immediately and thoroughly. If you're topping off your own vehicle, consider switching to a propylene-glycol-based antifreeze, which is far less toxic if a small amount is ingested.
Recognize hypothermia early — the signs escalate in this order: shivering (the earliest and most treatable stage), then lethargy and weakness, then stiff or slow-moving limbs, then shallow and slowed breathing, with cold ears and paw pads present throughout. A cat showing lethargy plus cold extremities needs warming and a vet, not a wait-and-see approach. If you find a hypothermic cat: wrap it in warm — not hot — towels or blankets (a towel-wrapped water bottle with warm, not scalding, water works if you have nothing else) and get to an emergency vet immediately. Warm gradually; rapid temperature swings can cause additional physiological shock.
Frostbite shows up on the extremities first — ear tips, tail tip, and paw pads are most exposed. Look for skin that's pale, grayish, or has a bluish tint, and note that swelling often appears only after the area starts to rewarm, not immediately. Frostbitten tissue is fragile: don't rub or massage it, as this causes additional tissue damage. Wrap the area loosely and get the cat to a vet promptly — some frostbite is reversible if caught early, but the window closes fast.
For a colony you're managing: winterizing shelters and upping food/water access in October or November, before the first hard freeze, gives cats time to establish the shelter as part of their routine before they need it under duress. Cats that already know where the warm, dry spot is will use it reflexively when temperatures crash.