A baby’s room should be kept between 68°F and 72°F (20°C to 22°C) for safe, comfortable sleep. Some guidelines, including those from the UK’s Lullaby Trust, recommend a slightly cooler range of 61°F to 68°F (16°C to 20°C). The key principle across all guidance is the same: cooler is safer than warmer, because overheating raises the risk of Sudden Infant Death Syndrome (SIDS).
Why Temperature Matters for Safe Sleep
Babies can’t regulate their body temperature the way adults can. Their small bodies heat up faster and lose heat faster, which makes the surrounding room temperature a real safety concern, not just a comfort preference. Overheating during sleep increases the risk of SIDS, and it’s one of the few risk factors parents can directly control.
The connection between overheating and SIDS isn’t fully understood, but the association is consistent enough that every major pediatric health organization includes room temperature in its safe sleep guidance. Keeping the room on the cool side, dressing your baby in light layers, and skipping heavy blankets are all part of the same protective strategy.
How to Check if Your Baby Is Too Hot or Cold
A room thermometer is the easiest way to monitor the nursery, but the number on the thermometer doesn’t tell the whole story. Your baby’s own body gives you the most useful feedback. To check, place your hand on your baby’s chest, stomach, or the back of their neck. That skin should feel warm but not hot or sweaty.
Signs your baby is overheating include:
- Flushed or red cheeks
- Skin that feels hot to the touch on the chest or back
- Sweating, especially around the head and neck
- Heat rash
If your baby is too cold, their stomach, back, or neck will feel cool rather than warm. Cold hands and feet alone aren’t a reliable sign, since infant extremities tend to run cool naturally due to immature circulation. Always check the torso.
What Your Baby Should Wear to Bed
The general rule is to dress your baby in one more layer than you would need to feel comfortable in the same room. In a room at 68°F to 72°F, that typically means a onesie underneath a medium-weight sleep sack. Loose blankets are not recommended for infants because of suffocation risk, so a wearable sleep sack is the safest way to add warmth.
Sleep sacks are rated using a system called TOG, which measures thermal resistance. Higher TOG numbers mean more warmth. Here’s a practical breakdown:
- 75°F to 81°F (warm room): A 0.2 TOG sleep sack, which is essentially a thin layer of fabric. A diaper and short-sleeve onesie underneath is usually enough.
- 68°F to 75°F (comfortable room): A 1.0 TOG sleep sack with a long-sleeve onesie.
- 64°F to 72°F (cool room): A 1.5 TOG sleep sack with a long-sleeve onesie or light pajamas.
- 61°F to 68°F (cold room): A 2.5 TOG sleep sack with warmer pajamas underneath.
- Below 61°F: A 3.5 TOG sleep sack, the warmest option, with layered clothing underneath.
Never cover your baby’s head with a hat for sleep. Babies release excess heat through their heads, and covering it can trap warmth and contribute to overheating.
Keeping the Room Cool in Summer
Summer heat and heatwaves can push a nursery well above the safe range, especially in homes without air conditioning. If you have AC, setting it to keep the room around 68°F to 72°F works well. If you don’t, a few practical steps can help.
Place the crib or bassinet in the coolest room of the house, which is usually a ground-floor room that doesn’t get direct afternoon sun. Close blinds or curtains during the hottest part of the day to block radiant heat. A fan can help circulate air, but point it away from your baby rather than blowing directly on them, and keep it out of reach.
Fan use during infant sleep has actually been studied for its effect on SIDS risk. A 2008 study found that running a fan in the room was associated with a 72% reduction in SIDS risk. The likely explanation is that air circulation prevents carbon dioxide from pooling around a baby’s nose and mouth. The protective effect was strongest in warmer rooms, which makes a fan especially worthwhile during hot weather.
On extremely hot days, strip your baby down to just a diaper and a thin 0.2 TOG sleep sack. If indoor temperatures stay dangerously high even with fans, consider spending the hottest hours at a friend’s air-conditioned home or a public building.
Keeping the Room Warm in Winter
In colder months, the temptation is to crank up the heat or pile on extra blankets. Resist both. A room at 68°F is perfectly warm enough for a baby in an appropriate sleep sack, and going higher increases overheating risk. If your home tends to run cold, layer your baby’s clothing underneath a higher-TOG sleep sack rather than adding blankets, pillows, or stuffed animals to the crib.
Space heaters can be hazardous around infants, both as a fire risk and because they can create hot spots in the room that don’t match what the thermometer reads. If you use one, keep it well away from the crib and turn it off before placing your baby down to sleep.
Humidity in the Nursery
Temperature gets most of the attention, but humidity matters too. The ideal relative humidity for a baby’s room is between 35% and 50%. Air that’s too dry can irritate your baby’s nasal passages and skin, while air that’s too humid encourages dust mites, mold, and allergens, all of which can trigger coughing and breathing difficulties.
A simple hygrometer (often built into digital room thermometers) lets you track humidity alongside temperature. In dry winter months, a cool-mist humidifier can bring levels up. In humid summer conditions, air conditioning or a dehumidifier keeps things in range. Clean humidifiers regularly to prevent mold growth inside the unit itself.
Room Sharing and Placement
For the first six months, placing your baby’s crib or bassinet in your bedroom is recommended as a protective measure against SIDS. This also makes it easier to monitor whether your baby seems too warm or too cold during the night without relying solely on a monitor. Position the crib away from direct heat sources like radiators, heating vents, and sunny windows, and away from drafts from exterior doors or single-pane windows.