The ideal room temperature for a newborn is 68 to 72°F (20 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). The recommendation holds year-round, regardless of season.
Why Newborns Are Sensitive to Room Temperature
Babies lose heat much faster than adults. They have a high ratio of body surface area to body mass, meaning more skin is exposed relative to their size. Their skin is thinner, their blood vessel control is less developed, and they can’t shiver effectively to warm up. Newborns do have a special type of fat called brown fat, located around the neck, shoulders, and kidneys, that generates heat when their body temperature drops. But this system has limits, especially in premature infants who have less of this fat stored.
On the flip side, babies also can’t cool themselves well. They can’t kick off blankets, adjust clothing, or sweat as efficiently as older children. This means the room you put them to sleep in has an outsized effect on their body temperature compared to what you’d experience yourself.
Overheating and SIDS Risk
Overheating during sleep increases a baby’s risk of SIDS. The connection is well established: when a baby gets too warm, their arousal responses can be suppressed, making it harder for them to wake up if breathing is compromised. The CDC and Mayo Clinic both emphasize keeping babies from getting too hot, avoiding head coverings, and skipping loose blankets in the crib.
A fan in the room can make a meaningful difference. A study comparing 185 SIDS cases with 312 control infants found that running a fan during sleep was associated with a 72% reduction in SIDS risk. The protective effect was even stronger in riskier sleep situations, such as warm rooms, closed windows, or side sleeping. The fan likely helps by circulating air and preventing pockets of exhaled carbon dioxide from collecting around the baby’s face. An open window showed a similar trend, though the results weren’t statistically significant.
Signs Your Baby Is Too Hot
You can’t always tell just by touching your baby’s hands or feet, which tend to run cool naturally. Instead, feel the back of the neck or chest. If the skin there feels hot or clammy, your baby is likely too warm. Other signs to watch for:
- Flushed or red skin
- Sweating or damp hair (though some overheated babies don’t sweat at all)
- Fussiness or restlessness that doesn’t have another obvious cause
- Rapid breathing or elevated heart rate
- Unusual sleepiness or limpness
If you notice several of these together, remove a layer of clothing or lower the room temperature and check again in a few minutes.
How to Dress Your Baby for Sleep
The right sleepwear depends on how warm the room actually is. Sleep sacks and wearable blankets are rated using a system called TOG, which measures thermal resistance. Higher TOG means more warmth. Here’s a practical guide:
- 75 to 81°F (24 to 27°C): A 0.2 TOG sleep sack or just a onesie. This is a warm room, so keep it minimal.
- 68 to 75°F (20 to 24°C): A 1.0 TOG sleep sack over a bodysuit. This is the sweet spot for most nurseries.
- 64 to 72°F (18 to 22°C): A 1.5 TOG sleep sack, possibly with a long-sleeve layer underneath.
- 61 to 64°F (16 to 18°C): A 2.5 TOG sleep sack with warmer pajamas.
- Below 61°F (below 16°C): A 3.5 TOG sleep sack with layers. At this point, consider raising the room temperature rather than adding more clothing.
A good rule of thumb: dress your baby in one more layer than you’d wear comfortably in the same room. Never cover a baby’s head while sleeping, as a significant amount of heat escapes through the head, and coverings increase suffocation risk.
Keeping the Room at the Right Temperature
Guessing the temperature in a room is surprisingly unreliable. The Lullaby Trust, a UK safe-sleep organization, recommends placing a room thermometer in the room where your baby sleeps. Digital nursery thermometers are inexpensive and many baby monitors include one built in. Place it near the crib at roughly the same height as the mattress, away from windows, heating vents, or direct sunlight, all of which can give a misleading reading.
In summer, a fan or air conditioner can bring the temperature into range. In winter, central heating often pushes rooms above 72°F, especially at night. If you can’t control the thermostat precisely, it’s better to keep the room slightly cool and add a layer of clothing than to overheat the space. Portable space heaters are a fire risk and can create hot zones in a room, so they’re best avoided in a nursery if possible.
If your home runs warm and you can’t easily get the room below 75°F, use the lightest sleep sack available (0.2 TOG or a simple cotton swaddle), run a fan, and check your baby’s chest periodically during the night. Conversely, if your home dips below 65°F, a warmer sleep sack is safer than adding loose blankets to the crib.