Babies sleep best in a room kept between 68 and 72°F (20 to 22°C). That narrow range helps infants maintain a stable body temperature without overheating or getting too cold, both of which disrupt sleep and, in the case of overheating, carry serious safety risks.
Why Temperature Matters More for Babies
Adults can kick off blankets, pull up covers, or simply sweat efficiently when a room is too warm. Babies can’t do any of that well. Their bodies are still developing the ability to regulate internal temperature, and one of the main ways they release excess heat is through their face. This is part of why back sleeping is so important: when a baby sleeps face-down, that cooling mechanism is blocked.
Overheating is a recognized risk factor for SIDS. A 30-year Canadian study of 196 SIDS cases found a clear link between higher environmental temperatures and infant deaths, particularly in babies aged 3 to 12 months. On days when outdoor temperatures exceeded about 84°F (29°C), the risk of SIDS was nearly three times higher than on 68°F (20°C) days. Keeping the nursery in that 68 to 72°F window reduces thermal stress and gives your baby’s body less work to do overnight.
Signs Your Baby Is Too Hot
A room thermometer is helpful, but your baby’s body gives you direct feedback. Check the skin on your baby’s chest, back, or the nape of their neck. If it feels hot or damp, the room is too warm or they’re overdressed. Other signs of overheating include:
- Sweating, especially around the neck, back, and underarms
- Heat rash, which looks like small red bumps on the skin
- Rapid breathing or unusual fussiness
- Restless, fragmented sleep with frequent waking
- Lethargy or becoming unusually quiet
A body temperature above 100.4°F (38°C) suggests your baby is genuinely overheating and not just warm.
Signs Your Baby Is Too Cold
Cold hands and feet on a baby are normal and not a reliable sign of being underdressed. Instead, touch their tummy or back. The skin there should feel warm but not hot. If it feels cool, your baby needs an extra layer. True signs of a baby being too cold include slow breathing, pale or cool-toned skin, and shivering, though very young infants don’t shiver the way older children do.
How to Dress Your Baby for Sleep
Loose blankets, pillows, and weighted swaddles don’t belong in a crib. The safest sleep surface is a firm mattress with nothing but a fitted sheet. That means temperature control comes down to what your baby wears, and sleep sacks are the go-to solution.
Sleep sacks are rated using a system called TOG, which measures warmth. Here’s a simple guide based on nursery temperature:
- Above 75°F (24°C): 0.5 TOG or lower, a lightweight layer
- 68 to 74°F (20 to 23°C): 1.0 TOG, a medium-weight layer
- 61 to 67°F (16 to 20°C): 2.5 TOG, a heavier layer
- Below 61°F (16°C): 3.5 TOG, the warmest option
A good rule of thumb: dress your baby in one more layer than you’d wear comfortably in the same room. If you’re fine in a t-shirt, your baby likely needs a onesie plus a light sleep sack.
Using a Fan in the Nursery
A fan won’t lower the actual air temperature, but it circulates air around the crib, and that turns out to matter. One study found that running a fan in a baby’s room reduced the risk of SIDS by 72 percent. The likely reason is that moving air prevents pockets of exhaled carbon dioxide from collecting near a baby’s face. The protective effect was even stronger in warmer rooms, where SIDS risk is already elevated. A simple oscillating fan pointed away from the crib (not blowing directly on your baby) is an easy, low-cost safety measure.
Keeping the Nursery Comfortable Year-Round
Maintaining 68 to 72°F is straightforward in spring and fall, but summer heat and winter cold can make it tricky. A few practical strategies help.
Position the crib away from windows and heating vents. Windows can let in drafts in winter and radiant heat in summer, and heating vents create uneven temperatures that a room thermometer across the room won’t catch. The goal is consistent, even warmth where the baby actually sleeps.
In summer, air conditioning or a fan can keep the room from climbing too high. If you don’t have central air, a window unit set to 70°F in the nursery works well. In winter, avoid space heaters placed close to the crib, and resist the urge to pile on extra layers. A properly rated sleep sack and footie pajamas handle cold nights better and more safely than blankets.
Humidity and Air Quality
Temperature isn’t the only factor in comfortable sleep. Humidity between 35 and 50 percent keeps your baby’s airways comfortable. When humidity drops below 35 percent, which is common in heated homes during winter, dry air can cause nosebleeds, dry skin, and irritated breathing passages. Above 50 percent, the air can trigger coughing and make breathing harder, while also encouraging mold growth. A simple hygrometer (often built into nursery thermometers) lets you monitor both numbers at a glance, and a cool-mist humidifier can bring dry winter air back into range.