For most nurseries kept between 68 and 72°F, a baby sleeps safely and comfortably in a one-piece pajama (a “onesie” or footed sleeper) paired with a wearable blanket, also called a sleep sack. The exact combination depends on your room temperature, the season, and your baby’s age. Getting it right matters: loose blankets, hats, and too many layers all pose safety risks.
The Safest Setup for Sleep
The core rule is simple: no loose bedding in the crib. That means no blankets, pillows, bumper pads, or stuffed animals. A wearable blanket or sleep sack is the safe alternative, keeping your baby warm without anything that could cover their face or bunch around their head. Products labeled as “weighted,” including weighted swaddles, sleep sacks, and blankets, are not safe for infants.
Hats should not be worn indoors for sleep. The American Academy of Pediatrics advises against putting hats on infants when indoors (except during the first hours after birth or in a NICU), because the benefit for preventing cold is minimal and the risk of overheating is real. Your baby loses excess heat through their head, and covering it interferes with that process.
What to Dress Your Baby in by Room Temperature
Sleep sacks come with a TOG rating, which measures thermal resistance. A higher TOG means more warmth. Here’s how to match your room temperature to the right TOG and clothing layers underneath:
- 75°F to 81°F (warm summer nights): A 0.2 TOG sleep sack over just a short-sleeve bodysuit, or even a diaper alone. In genuinely hot weather, a single lightweight layer without a sleep sack is fine.
- 68°F to 75°F (typical nursery): A 1.0 TOG sleep sack over a short- or long-sleeve bodysuit.
- 64°F to 68°F (cool room): A 1.5 to 2.5 TOG sleep sack over a footed pajama or a bodysuit with a long-sleeve layer.
- Below 64°F (cold room): A 2.5 to 3.5 TOG sleep sack over a long-sleeve bodysuit and footed pajama.
These are starting points. Every baby runs a little warmer or cooler. The best way to check is to feel your baby’s chest or the back of their neck. Their hands and feet will almost always feel cool, and that’s normal. What you’re looking for is whether their torso feels comfortably warm, hot, or clammy.
Signs Your Baby Is Too Hot
Overheating is a bigger risk than being slightly cool, and it’s linked to unsafe sleep outcomes. Watch for skin that feels hot to the touch, flushed or red cheeks, damp hair, and unusual fussiness or restlessness. Some babies overheat without visibly sweating, so skin temperature is a more reliable check than looking for sweat. If your baby’s chest feels hot or sticky, remove a layer or switch to a lower TOG sleep sack.
A sluggish, overly tired, or listless baby can also signal overheating that’s gone further than simple discomfort.
Swaddling: When to Start and When to Stop
Newborns often sleep better swaddled because it dampens the startle reflex that wakes them. A snug swaddle with arms tucked in is appropriate for the first weeks of life. But as soon as your baby shows signs of rolling over, swaddling becomes dangerous because it restricts their ability to push up or move their face away from the mattress.
Most babies start showing rolling signs between 2 and 6 months, though some begin as early as 8 weeks. The signals to watch for: pushing up on their hands during tummy time, lifting their legs and flopping them to the side, breaking free of the swaddle, or any actual rolling during play. When you see these, switch immediately to an arms-free sleep sack. There’s no safe grace period once rolling begins.
Choosing the Right Fabric
Cotton and bamboo viscose are the two most common fabrics for baby sleepwear, and they behave differently at night. Cotton breathes well and is widely available, but it absorbs moisture and holds onto it. If your baby sweats during sleep, cotton pajamas can stay damp, which leads to discomfort and sometimes skin irritation.
Bamboo viscose wicks moisture away from the skin and releases it more quickly, keeping your baby drier. It also adapts better to temperature shifts, staying cooler in warm rooms and warmer in cool ones. For babies who tend to run hot or who sweat easily, bamboo is generally the better choice. For a baby in a well-controlled room who doesn’t sweat much, cotton works perfectly well. Either way, avoid synthetic fabrics that trap heat and don’t breathe.
Quick Reference by Age
Your baby’s sleep wardrobe evolves as they grow. Here’s what that looks like in practice:
- Newborn to 8 weeks: Swaddle (not weighted) plus a bodysuit or footed sleeper underneath, adjusted for room temperature. No hat indoors.
- 2 to 6 months: Transition out of the swaddle as soon as rolling signs appear. Move to an arms-free sleep sack with a bodysuit or pajama underneath.
- 6 to 12 months: Sleep sack with age-appropriate pajamas. Most babies this age do well in a footed sleeper plus a 1.0 TOG sack in a standard nursery.
- 12 months and beyond: Many toddlers continue using sleep sacks, which remain a safe option. Some parents transition to a light blanket after 12 months, but a sleep sack eliminates the need.
Setting Up the Room
Clothing choices only work in context. The recommended nursery temperature is 68 to 72°F (20 to 22°C). A simple room thermometer near the crib takes the guesswork out of it. If your home runs warmer in summer and you don’t have air conditioning, strip down to a single light layer and use the lowest TOG sleep sack you can find, or skip the sack entirely and use just a short-sleeve bodysuit. In winter, it’s more effective to add a warmer sleep sack than to pile on extra clothing layers, which can bunch up and cause overheating in spots.
A fan circulating air in the room can help regulate temperature and has been associated with safer sleep environments, though it shouldn’t blow directly on your baby.