Babies lose body heat faster than adults, so it’s a valid concern. The quickest way to check is by touching your baby’s chest, belly, or the back of their neck. These areas should feel warm and dry. If the skin there feels cool, your baby needs an extra layer. The room itself should be between 61°F and 68°F (16–20°C), which feels cooler than most parents expect.
Why Babies Lose Heat So Quickly
Infants have a large surface area relative to their body weight, which means heat escapes through their skin much faster than it does from an adult’s body. They lose heat through four routes: evaporation from damp skin, direct contact with cool surfaces, radiant heat moving toward cooler walls or windows, and air currents passing over exposed skin. Adults compensate by shivering, but newborns can’t do that effectively. Instead, they rely on a special type of fat called brown fat, concentrated between the shoulder blades and around the organs, which burns calories to generate warmth without shivering.
This system works, but it comes at a cost. When a baby activates that heat production, it uses up extra oxygen and energy that would otherwise go toward growth and normal body functions. A baby who is consistently too cold at night is burning through calories to stay warm rather than using them to develop. That’s why getting the temperature right matters beyond simple comfort.
How to Tell If Your Baby Is Cold
Cold hands and feet are the sign most parents notice first, and most parents dismiss them as normal. They shouldn’t be ignored entirely. When a baby starts getting cold, the body narrows blood vessels in the hands and feet first to keep the core warm. Researchers have categorized it simply: a warm belly with warm feet means your baby’s temperature is fine, a warm belly with cold feet signals cold stress, and a cold belly with cold feet means your baby is already heading toward hypothermia.
So cold fingers and toes alone don’t mean your baby is in danger, but they do indicate the body is working to conserve heat. Check the torso next. Place your hand on your baby’s chest or stomach, or feel the back of their neck just below the hairline. If those areas feel cool or clammy, your baby needs more warmth. If they feel warm and dry, your baby is fine even if the toes are chilly.
Other signs of a cold baby include fussiness, unusually still or quiet behavior, and skin that looks mottled or slightly bluish, especially around the lips. A baby who wakes frequently and seems unsettled but isn’t hungry may simply be uncomfortable from the cold.
The Right Room Temperature
The recommended nursery temperature is 61–68°F (16–20°C). That range surprises many parents because it feels cool to an adult standing in the room. But babies sleep in layers and sleep sacks that trap warmth efficiently, and a slightly cool room is genuinely safer than a warm one.
A simple room thermometer near the crib is the easiest way to monitor this. Digital ones that track overnight highs and lows cost very little and take the guesswork out of dressing your baby. Keep the crib away from windows, exterior walls, radiators, and heating vents, all of which can create temperature pockets that don’t match the rest of the room.
Why Overheating Is the Bigger Risk
Parents tend to worry more about cold, but overheating is the more dangerous problem during sleep. Research has consistently linked excessive clothing, heavy bedding, and warm room temperatures to a higher risk of SIDS. One early study of 34 SIDS cases found that 19 of the babies were unusually hot or sweating when found, 14 had been in an unusually warm room, and 24 were excessively clothed or overwrapped.
The mechanism behind this involves how heat affects a sleeping baby’s ability to respond to breathing problems. Thermal stress can slow the heart rate, cause pauses in breathing, and reduce blood oxygen levels. At the same time, being too warm makes a baby harder to arouse from deep sleep and less responsive to those breathing disruptions. So even when overheating isn’t directly harmful on its own, it can compound other risk factors in dangerous ways.
Signs your baby is too hot include sweating (especially on the head and neck), flushed or red skin, damp hair, rapid breathing, and restless sleep. If your baby’s chest feels hot or sweaty, remove a layer.
What Your Baby Should Wear to Bed
The NHS recommends dressing your baby in one more layer than what you’d comfortably wear in the same room. If you’re comfortable in a T-shirt and sweater, your baby would be appropriately dressed in a bodysuit, a footed sleepsuit, and a light cardigan or sleep sack. If you feel chilly, your baby probably does too.
The American Academy of Pediatrics recommends against loose blankets, pillows, quilts, and comforters in the crib for the entire first year. These items pose suffocation and entrapment risks. Wearable blankets (sleep sacks) are the recommended alternative, keeping your baby warm without any loose fabric that could cover the face.
Sleep sacks are rated by TOG, a measure of thermal resistance. Higher TOG means more warmth. Here’s how to match the rating to your nursery temperature:
- Over 80°F (27°C+): 0.2 TOG, essentially a single thin layer
- 73–79°F (23–26°C): 0.5 TOG, a light muslin sleep sack
- 68–73°F (21–23°C): 1.0 TOG, a standard cotton sleep sack
- 61–68°F (16–20°C): 2.5 TOG, a quilted or fleece-lined sleep sack
- Below 60°F (under 16°C): 3.5 TOG, the warmest option available
Underneath the sleep sack, a long-sleeved bodysuit or footed sleepsuit is typical for cooler rooms. In warmer conditions, a short-sleeved bodysuit or even just a diaper may be enough. Cotton is generally the best fabric for the base layer because it breathes well and wicks moisture.
Managing Temperature Through the Night
Room temperature often drops in the early morning hours, which is when babies are most likely to get cold. If your home cools significantly overnight, a thermostat set to maintain the 61–68°F range prevents the room from dipping too low. Space heaters are risky near a crib and can also overheat a small room quickly.
Bed-sharing creates its own temperature problem. Research shows that bed-sharing infants are exposed to higher levels of thermal insulation from adult bedding, body heat, and duvets, and parents don’t compensate by reducing the baby’s clothing layers or lowering room temperature. The result is that bed-sharing babies consistently run warmer than babies sleeping alone in a crib.
If you’re checking on your baby during the night, do the chest or neck touch rather than relying on how the hands and feet feel. A quick check at your own bedtime and again if you happen to wake in the early hours covers the times when temperature shifts are most likely. Over the first few weeks, you’ll develop a sense for how your baby responds to different combinations of layers and room temperature, and the nightly adjustments become second nature.