The ideal room temperature for a baby’s sleep is between 68°F and 72°F (20°C to 22°C). This range keeps infants comfortable without raising the risk of overheating, which is a known risk factor for Sudden Infant Death Syndrome (SIDS). A few degrees in either direction is fine as long as your baby isn’t showing signs of being too hot or too cold.
Why Overheating Is the Bigger Danger
Parents tend to worry more about their baby being cold, but overheating is the more serious concern. Being too warm during sleep increases the risk of SIDS. The exact mechanism isn’t fully understood, but it likely involves the part of an infant’s brain that controls breathing and arousal from sleep. When a baby gets too hot, their ability to wake up in response to breathing problems may be impaired.
This is also why safe sleep guidelines emphasize keeping the crib bare. Thick quilts, lambskin, fluffy padding, pillows, and stuffed animals can all trap heat around a baby’s body in addition to posing suffocation risks. A firm, flat mattress with a fitted sheet is all you need in the crib.
How to Dress Your Baby for Sleep
Room temperature alone doesn’t determine whether your baby is comfortable. What they’re wearing matters just as much. Sleep sacks (wearable blankets) are rated using a TOG system, which measures thermal resistance. Here’s a general guide:
- 75°F to 81°F (24°C to 27°C): A 0.2 TOG sleep sack or just a onesie. This is a very lightweight layer.
- 68°F to 75°F (20°C to 24°C): A 1.0 TOG sleep sack over a short-sleeve bodysuit. The sweet spot for most nurseries.
- 64°F to 72°F (18°C to 22°C): A 1.5 TOG sleep sack, possibly with a long-sleeve bodysuit underneath.
- 61°F to 68°F (16°C to 20°C): A 2.5 TOG sleep sack with warmer pajamas.
- Below 61°F (16°C): A 3.5 TOG sleep sack with warm layers underneath.
Every baby runs a little different, so treat these as starting points. A baby who feels clammy at the chest in a 1.0 TOG sack at 72°F may do better with the lighter option.
How to Tell If Your Baby Is Too Hot or Too Cold
Don’t rely on your baby’s hands or feet to gauge their temperature. Infant extremities are often cool even when the rest of their body is perfectly warm. Instead, touch the back of their neck or their chest. That skin should feel warm but dry.
Signs of overheating include:
- Skin that feels hot to the touch, especially on the chest
- Flushed or red face
- Sweating or damp hair (though babies can overheat without sweating)
- Fussiness or restlessness
- Rapid breathing or elevated heart rate
- Unusual sluggishness or limpness
A baby who is too cold will typically feel cool on the chest and may be fussy, but this is far less common than overheating in homes with central heating. Adding one layer is usually enough to fix the problem.
Using a Fan in the Nursery
A fan can help in two ways: it keeps the air circulating and may reduce SIDS risk. A study published in the Archives of Pediatrics and Adolescent Medicine found that having a fan running in a baby’s room lowered SIDS risk by 72 percent. The likely explanation is that moving air prevents pockets of exhaled carbon dioxide from pooling around a baby’s face, reducing the chance of “rebreathing.”
Fans don’t actually cool the air, they just move it around. So if you’re worried about your baby getting chilled, the fan itself isn’t lowering the room temperature. Point it toward the ceiling or a wall rather than directly at the crib, and it will help circulate air without creating a draft on your baby.
Where to Place a Nursery Thermometer
Room temperature can vary by 2 to 4 degrees between the floor and ceiling, so placement matters. Put your thermometer at roughly the same height as your baby’s sleeping position, which for a crib is usually about 2 to 3 feet off the ground. Keep it about 3 feet away from the crib so your baby’s body heat doesn’t skew the reading. Avoid placing it near windows, heating vents, or exterior walls, all of which can give you a number that doesn’t reflect what your baby is actually experiencing.
Many baby monitors now include a built-in temperature sensor. These work fine as long as the monitor is positioned near the crib at a reasonable height rather than mounted high on a wall.
Humidity Matters Too
Temperature gets most of the attention, but the moisture level in your baby’s room affects their comfort and breathing. Boston Children’s Hospital recommends keeping indoor humidity between 35 and 50 percent. Air that’s too dry can cause congestion, dry skin, nosebleeds, and irritated airways. Air that’s too humid encourages dust mites, mold, and allergens, all of which can make breathing harder for a baby.
A simple hygrometer (often built into nursery thermometers) will tell you where you stand. In winter, when indoor air tends to dry out, a cool-mist humidifier can bring levels back into range. In summer or in humid climates, air conditioning or a dehumidifier keeps things from swinging too high.