The ideal room temperature for a newborn is between 68°F and 72°F (20°C to 22°C). This range keeps your baby comfortable without increasing the risk of overheating, which is a known risk factor for sudden infant death syndrome (SIDS). A room that feels slightly cool to you as an adult is generally just right for a sleeping baby.
Why Temperature Matters for Newborns
Newborns can’t regulate their body temperature the way older children and adults can. When a room is too warm, a baby’s risk of SIDS increases. The exact mechanism isn’t fully understood, but it likely involves the area of the infant brain that controls breathing and arousal from sleep. Overheating may interfere with a baby’s ability to wake up if breathing becomes compromised.
Cold rooms carry their own risks. Cold stress happens when a baby’s body has to burn extra calories just to stay warm, and it can begin even before the baby’s core temperature actually drops. In a newborn, this stress response increases metabolic rate and oxygen demand by two to three times the normal level. Over time, unrecognized cold stress diverts calories away from growth and can lead to low blood sugar. For premature babies or those with breathing difficulties, the consequences can be more serious, including reduced oxygen to tissues.
Signs Your Baby Is Too Hot
The best way to check is by touching the skin on your baby’s chest, back, or the back of their neck. These areas give a more accurate read than hands or feet, which tend to run cooler in newborns regardless of room temperature. If your baby’s torso feels hot or damp to the touch, they’re likely overdressed or the room is too warm.
Other signs to watch for:
- Sweating, especially around the neck, back, and underarms
- Heat rash, small red bumps on the skin in areas that stay warm
- Rapid breathing or unusual fussiness
- Lethargy, where the baby seems unusually quiet or difficult to rouse
If you notice any of these, remove a layer of clothing, adjust the thermostat, or both. Flushed cheeks alone aren’t always a concern, but combined with a hot torso or sweating, they suggest the baby needs to cool down.
Signs Your Baby Is Too Cold
A cold baby may feel cool to the touch on the chest or belly, not just the hands and feet. Fussiness and difficulty settling can be early signs. In more prolonged cases, a baby who is cold-stressed may become lethargic, feed poorly, or have mottled skin. Because cold stress burns through energy reserves quickly, a consistently chilly room can interfere with healthy weight gain over time.
How to Dress Your Baby for Sleep
The general rule: dress your baby in one more layer than you’d wear comfortably in the same room. A onesie plus a wearable blanket (sleep sack) is a reliable starting point for a room in the 68°F to 72°F range. Loose blankets, quilts, and pillows should stay out of the crib entirely.
Sleep sacks are rated using a system called TOG, which measures thermal resistance. Higher TOG numbers mean more warmth. Here’s a practical guide:
- 71°F and above: A lightweight 0.2 or 0.3 TOG sleep sack, or just a onesie
- 67°F to 75°F: A 1.0 TOG sleep sack over a short-sleeve bodysuit
- 59°F to 69°F: A 2.5 TOG sleep sack with a long-sleeve layer underneath
- 53°F to 65°F: A 3.5 TOG sleep sack with warmer underlayers
Notice that the ranges overlap. That’s normal. Use your baby’s skin temperature as the tiebreaker. If the room is 69°F and your baby’s chest feels warm and dry in a 1.0 TOG sack, there’s no reason to move up. Never cover your baby’s head for sleep, as a significant amount of heat escapes through the head, and head coverings increase overheating risk.
Setting Up the Nursery
A simple room thermometer placed near the crib (but out of reach) takes the guesswork out of temperature monitoring. Many baby monitors now include a temperature sensor, which works just as well. Check it at bedtime and again during the early morning hours, when rooms tend to cool down the most.
Fans can help. Gentle air circulation in the room has been associated with reduced SIDS risk in some studies, likely because it prevents pockets of warm, stale air from forming around the baby’s face. A ceiling fan on low or a small fan pointed away from the crib, not directly at the baby, is enough.
Humidity matters too. Boston Children’s Hospital recommends keeping indoor humidity between 35% and 50%. Air that’s too dry can irritate a newborn’s airways and cause coughing, while air that’s too humid encourages mold growth and can also make breathing harder. A simple hygrometer (often built into room thermometers) lets you track this alongside temperature. In dry winter months, a cool-mist humidifier can bring levels into the right range.
Seasonal Adjustments
In summer, air conditioning is fine as long as the vent isn’t blowing directly onto the crib. Keep the thermostat in the 68°F to 72°F sweet spot, and dress your baby in lighter layers. On hot nights without air conditioning, a fan and a low-TOG sleep sack (or even just a diaper and a thin cotton onesie) can work.
Winter requires a bit more attention. Homes with central heating sometimes overshoot at night, pushing nursery temperatures above 72°F. Others cool off significantly in the early morning hours. Checking the room temperature a few times during the first couple of nights in a new setup will give you a sense of how your home behaves. If the room drops into the low 60s overnight, a warmer sleep sack is a safer solution than adding blankets.