The answer depends entirely on the pig’s age and size. Newborn piglets can die within minutes if temperatures drop below 2°C (36°F), while healthy adult sows tolerate conditions well below freezing before experiencing real stress. Understanding these thresholds, and the warning signs that come before serious trouble, can prevent losses and keep your animals comfortable through winter.
Temperature Thresholds by Age and Size
Every pig has a lower critical temperature, the point below which its body has to burn extra energy just to stay warm. The younger and smaller the pig, the higher that threshold sits.
Newborn piglets need ambient temperatures between 27°C and 35°C (roughly 80°F to 95°F) to thrive. Their bodies carry almost no fat reserves, and they lose heat rapidly through their skin. Once temperatures fall below 16°C (61°F), you risk losing piglets. Below 2°C (36°F), death can come within minutes. This is the most dangerous window in a pig’s life for cold exposure.
Newly weaned pigs still need warmth, though not as much. The ideal air temperature for a freshly weaned pig is around 28°C (83°F), with floor or mat temperatures closer to 35°C (95°F). These requirements start dropping about a week after weaning as the piglets adjust and grow. Nursery pigs in the 14 to 34 kg range can handle progressively cooler conditions, but drafts remain a serious threat at this stage.
Growing and finishing pigs, from roughly 34 kg up to market weight, are far more cold-tolerant. Their lower critical temperature sits somewhere around 10°C to 15°C (50°F to 59°F) depending on housing, bedding, and whether they’re in groups. Adult sows and boars are the hardiest, generally comfortable down to around 5°C (41°F) or even lower in dry, draft-free conditions with adequate bedding and feed.
Signs Your Pigs Are Too Cold
Pigs tell you they’re cold before it becomes an emergency, if you know what to look for. The two clearest behavioral signals are shivering and huddling. Research on outdoor-housed piglets found that for every 1°C drop in temperature, the likelihood of shivering increased by about 15%, and the chance of the entire litter huddling into a single tight group increased by 19%. These aren’t subtle changes. A cold litter looks noticeably different from a comfortable one.
Piglets also press themselves against the sow more as temperatures drop. While this seems like a natural solution, it’s actually one of the biggest risk factors for crushing deaths. Sows rolling onto piglets that are huddled too close is a leading cause of piglet mortality in cold weather. If you notice piglets consistently piled against the sow rather than spread out or using a creep area, the environment is too cold.
In older pigs, watch for piling behavior (multiple pigs stacking on top of each other), reluctance to move, and reduced feed intake. A pig that’s shivering and refusing to get up to eat is well past the point of mild discomfort.
Wind and Moisture Make It Worse
The thermometer on the barn wall doesn’t tell the whole story. Air movement and humidity both change the temperature a pig actually experiences. Even a modest draft lowers the effective temperature significantly, meaning a barn that reads 15°C can feel much colder to a pig standing in moving air. This is the same wind chill concept that applies to humans, and it hits young pigs especially hard because of their high surface-area-to-weight ratio.
Wet conditions compound the problem. A pig lying on damp bedding or a wet concrete floor loses heat far faster than one on dry material. Condensation from poor ventilation creates the same issue, coating surfaces with moisture that pulls warmth away from any animal in contact with it. Cold and dry is manageable. Cold and wet is dangerous.
How Bedding Changes the Equation
Good bedding is one of the cheapest and most effective cold-weather tools available. The difference it makes is dramatic. Research measuring heat loss from newborn piglets found that just 2.5 cm (about 1 inch) of straw on a concrete floor was equivalent to raising the floor temperature by 15°C. The same thickness of wood wool provided a 19°C boost, and wood shavings on concrete added about 9°C of effective warmth.
On bare concrete, roughly 15% of a newborn pig’s total heat loss goes straight through the floor. On a wood surface, that drops to 6%. On insulated flooring like expanded polystyrene, it’s just 2%. For piglets especially, the floor matters almost as much as the air temperature. If you can’t heat the entire room, insulating the floor where piglets rest gives you the most return for the least cost.
Supplemental Heat for Piglets
In farrowing areas, heat lamps are the standard solution for keeping piglets warm without overheating the sow. A typical setup uses a 100 to 250 watt lamp suspended 60 to 120 cm (2 to 4 feet) above the floor in the creep area. The closer the lamp hangs to the floor, the warmer that spot gets, but the smaller the heated zone. You regulate temperature by adjusting height rather than wattage.
The goal is to create a warm microclimate where piglets can retreat without needing to press against the sow. If piglets consistently ignore the creep area and cluster near the sow instead, the lamp is either too high, too far from where piglets naturally rest, or not providing enough warmth. If they’re spread in a ring far from the lamp, it’s too hot. Comfortable piglets will lie loosely under or near the heat source.
Feed Requirements Rise in Cold Weather
When pigs are below their comfort zone, they burn extra calories to generate body heat. This has a direct, measurable cost. For growing and finishing pigs between 20 and 100 kg, the best estimates suggest an extra 30 to 40 grams of feed per pig per day for every degree Celsius below the lower critical temperature. That works out to roughly 1.4% more feed per degree of cold stress.
To put that in practical terms: if your finishing barn normally sits at 18°C but drops to 8°C during a cold snap, and your pigs’ lower critical temperature is around 15°C, they’re experiencing about 7 degrees of cold stress. That means each pig needs roughly 210 to 280 grams of extra feed per day just to maintain the same growth rate. Multiply that across a barn of several hundred pigs over a few weeks of winter, and the feed cost adds up fast. In many operations, investing in better insulation or draft control pays for itself in saved feed alone.
Ventilation Still Matters in Winter
One of the most common winter mistakes is sealing up a barn too tightly to trap heat. Even in the coldest weather, pigs need a minimum level of fresh air exchange to control moisture, ammonia, and airborne pathogens. A finishing pig needs at least 10 cubic feet per minute (cfm) of airflow, while a sow with a litter needs about 20 cfm. Nursery pigs require just 2 to 3 cfm per pig.
Under-ventilated barns quickly develop high humidity and condensation. This creates exactly the cold, wet conditions that make temperature stress worse while also promoting bacterial growth, mildew, and respiratory disease. The goal in winter is to bring in just enough fresh air to keep surfaces dry and air quality acceptable, without creating drafts at pig level. Inlet placement and baffling matter more in winter than any other season.
Water Temperature in Winter
Cold drinking water is an overlooked source of stress. Pigs that have to drink near-freezing water use body heat to warm it internally, which increases their energy needs. Research on weaned piglets found that providing water at around 30°C (86°F) during cold weather improved gut health and nutrient absorption compared to cold water. While heating water to that degree isn’t always practical, preventing water lines from freezing and keeping water above at least 10°C (50°F) reduces unnecessary thermal stress and encourages pigs to drink enough to stay properly hydrated.