A baby’s room should be kept between 68°F and 72°F (20°C to 22°C) for safe, comfortable sleep. The Lullaby Trust, a leading authority on infant sleep safety, recommends a range of 60°F to 68°F (16°C to 20°C), which is slightly cooler than most parents expect. In practice, anything between 65°F and 72°F works well for most homes and climates, as long as you dress your baby appropriately for the temperature.
Why Room Temperature Matters for Babies
Babies can’t regulate their body temperature the way adults can. They have a higher ratio of skin surface area to body weight, meaning they lose heat faster when it’s cold and absorb it faster when it’s warm. Newborns rely on a special type of fat called brown fat, stored around the neck and shoulders, to generate warmth when they get chilly. But this system has limits, and babies can’t do much to cool themselves down. They don’t sweat efficiently, and they obviously can’t kick off blankets or adjust a thermostat.
This is why overheating during sleep is a recognized risk factor for sudden infant death syndrome (SIDS). The Mayo Clinic lists being too warm while sleeping as a factor that can increase a baby’s risk. Keeping the room on the cooler side, and dressing your baby in layers rather than piling on blankets, is one of the simplest things you can do to reduce that risk.
Signs Your Baby Is Too Hot or Too Cold
A room thermometer helps, but your baby’s body gives you the most reliable feedback. The best spot to check is the back of the neck or the chest. If the skin there feels hot, sweaty, or clammy, your baby is too warm. If it feels cool to the touch, add a layer.
Don’t rely on hands and feet alone. Babies often have cool hands and feet even when the rest of their body is perfectly warm, because their circulation prioritizes the core. Other signs of overheating include:
- Flushed or red skin, especially on the face
- Damp hair
- Fussiness or restlessness that’s hard to explain
- Unusual sleepiness or limpness
- Rapid breathing or a fast heart rate
Some babies overheat without sweating at all, so don’t assume dry skin means a comfortable temperature.
How to Dress Your Baby for Sleep
The safest approach is to skip loose blankets entirely and use a wearable blanket, often called a sleep sack. Sleep sacks are rated by a number called TOG, which measures how much warmth the fabric provides. The higher the TOG, the warmer the sack. Matching the right TOG to your room temperature keeps your baby comfortable without adding loose bedding to the crib.
Here’s a general guide:
- 75°F to 81°F (warm rooms or summer): 0.2 TOG, essentially a thin muslin layer. A diaper alone or a short-sleeve onesie underneath.
- 68°F to 75°F (typical indoor range): 1.0 TOG. A long-sleeve onesie underneath usually works well.
- 64°F to 72°F: 1.5 TOG with a long-sleeve bodysuit.
- 61°F to 68°F (cooler rooms): 2.5 TOG. You can add a footed pajama underneath.
- Below 61°F: 3.5 TOG, the warmest option, with warm pajamas underneath.
Never cover your baby’s head while they sleep. Babies release a significant amount of excess heat through their heads, and covering it traps that warmth.
Keeping the Room at the Right Temperature
In summer, a fan can help circulate air without blowing directly on the baby. Air conditioning set to 68°F to 72°F is perfectly fine. In winter, central heating often pushes rooms above the ideal range, so a thermometer in the nursery is worth having so you can adjust the thermostat or crack a door.
Humidity matters too. Boston Children’s Hospital recommends keeping indoor humidity between 35% and 50%. Air that’s too dry can irritate your baby’s airways and cause coughing, while air that’s too humid encourages mold growth. A simple hygrometer (often built into nursery thermometers) lets you keep an eye on both numbers at once. In dry winter months, a cool-mist humidifier can bring the level into a comfortable range.
Place the crib away from direct sunlight, heating vents, radiators, and exterior walls that may get cold. These can create microclimates around the sleep space that don’t match what the room thermometer reads.
Adjusting Temperature When Your Baby Is Sick
When a baby has a fever, the instinct is to bundle them up. It’s better to do the opposite. Texas Children’s Hospital advises dressing a feverish child lightly, because excess clothing traps body heat and can push their temperature even higher. Keep the room in the same 68°F to 72°F range and reduce layers rather than adding them. Babies are especially prone to fevers caused by overdressing or hot environments, since their temperature regulation is still developing.
If your baby feels hot but isn’t sick, the room itself may be the problem. Check the thermostat, feel the back of their neck, and remove a layer before assuming they have a fever.
Quick Reference by Room Temperature
- Below 64°F: Too cold for most babies. Use a high-TOG sleep sack with warm pajamas, and consider raising the thermostat.
- 64°F to 68°F: On the cool side but safe. A 2.5 TOG sleep sack with a long-sleeve layer works well.
- 68°F to 72°F: The sweet spot for most nurseries. A 1.0 TOG sack with a onesie is usually enough.
- 72°F to 76°F: Warm but manageable. Use a lightweight 0.2 TOG sack or a single thin layer.
- Above 76°F: Risk of overheating increases. A diaper with a thin muslin sack, a fan for air circulation, and close monitoring are all reasonable steps.