The simplest rule for dressing a newborn for sleep: one layer more than what you’d wear comfortably in the same room. In practice, that usually means a bodysuit plus a wearable blanket (sleep sack), adjusted up or down based on room temperature. Getting the combination right keeps your baby warm enough to sleep soundly without the overheating risk that loose blankets and excess layers can create.
Start With Room Temperature
The ideal nursery temperature for a newborn falls between 61°F and 68°F (16–20°C), according to The Lullaby Trust. Many homes, especially in warmer climates or summer months, sit closer to 68–72°F, which is still perfectly safe with lighter layers. A simple room thermometer near the crib gives you a reliable starting point every night.
Room temperature matters more than the season. A winter nursery with the heat cranked to 74°F needs lighter sleepwear than a cool spring night at 64°F. Check the thermometer, then dress accordingly.
What to Dress Your Baby In at Every Temperature
Sleep sacks use a measurement called a TOG rating to indicate warmth. The higher the TOG number, the thicker and warmer the fabric. Here’s how to match your baby’s layers to the room:
- 75–81°F (24–27°C): Diaper only or a short-sleeve bodysuit under a 0.2–0.5 TOG sleep sack.
- 72–75°F (22–24°C): Short-sleeve bodysuit under a 0.5–1.0 TOG sleep sack.
- 68–72°F (20–22°C): Long-sleeve bodysuit under a 1.0–1.5 TOG sleep sack.
- 64–68°F (18–20°C): Long-sleeve bodysuit plus light pants under a 1.5–2.5 TOG sleep sack.
- 61–64°F (16–18°C): Long-sleeve bodysuit plus footed pajamas under a 2.5–3.5 TOG sleep sack.
If the room dips below 61°F, you can layer a long-sleeve bodysuit under footed pajamas and use a 3.5 TOG sleep sack. But at that point, it’s worth considering whether the room itself is too cold and adjusting the thermostat instead of piling on layers.
Why Sleep Sacks Over Blankets
The American Academy of Pediatrics recommends keeping all loose bedding out of the crib until at least 12 months. Blankets can shift over a baby’s face and create a suffocation risk. A 2019 analysis found that infant sleep sacks are “as safe, if not safer, than other bedding” for preventing sudden infant death syndrome (SIDS). Sleep sacks provide the warmth and comfort of a blanket while staying securely in place.
One important detail: your baby’s arms should stay free inside a sleep sack. If a baby rolls onto their stomach, free arms allow them to push up and reposition. This is why sleep sacks are designed with open armholes rather than fully enclosing the baby.
Swaddling in the Early Weeks
For the first weeks of life, many parents swaddle their newborn with arms snug against the body. Swaddling helps calm the startle reflex, which can wake babies during light sleep. It’s safe during this brief window, but you need to stop as soon as your baby shows signs of rolling, which typically happens between 2 and 6 months.
Signs it’s time to transition out of the swaddle include: rolling or attempting to roll during playtime, pushing up on hands during tummy time, consistently breaking free of the swaddle, or lifting and flopping their legs to one side. Once you see any of these, switch to a sleep sack with arms free. Some transitional products have detachable arm wings that make the shift more gradual.
Skip the Hat Indoors
Newborns often leave the hospital wearing a knit cap, which can lead parents to keep one on at home. The AAP advises against placing hats on infants indoors except during the first hours after birth or in the NICU. A baby’s head is a primary way their body releases excess heat. Covering it during sleep increases the risk of overheating, and there’s little benefit for preventing cold once a baby is in a temperature-controlled home.
How to Check if Your Baby Is Too Warm
The quickest check is to touch the back of your baby’s neck or their chest. These areas give you a more accurate read on core temperature than hands or feet, which tend to feel cool even when a baby is perfectly comfortable. Warm, dry skin at the neck means you’ve nailed the layering. Hot or sweaty skin means you should remove a layer.
Other signs of overheating include flushed or red skin, damp hair, fussiness or restlessness, and unusual lethargy. Some babies develop heat rash, which looks like tiny red bumps in skin folds, around the neck, or on the bottom. Overheating is a known risk factor for SIDS, so when you’re unsure between adding or removing a layer, slightly cooler is the safer choice.
Choosing the Right Fabric
Cotton and bamboo viscose are the two most common fabrics for newborn sleepwear, and they perform differently overnight.
Cotton is breathable and widely available, but it absorbs moisture without releasing it quickly. If your baby sweats during sleep, cotton can stay damp and feel clammy. It also tends to hold heat in warmer rooms, which makes it a better pick for cooler temperatures where that retention works in your favor.
Bamboo viscose is softer, more breathable, and better at wicking moisture away from skin. It naturally adjusts to the environment, keeping babies warmer on cool nights and cooler in the heat. If your baby runs hot or you live in a warm climate, bamboo is generally the more comfortable option. It also works well year-round because of that temperature-regulating quality.
Whichever fabric you choose, look for sleepwear that fits snugly. Loose, oversized clothing can bunch up around your baby’s face the same way a blanket would. Sleepwear should fit close to the body, with no dangling ties, strings, or hoods.
Practical Night-to-Night Approach
Rather than memorizing charts, build a simple system. Keep two or three sleep sacks in different TOG ratings: a lightweight one (0.5–1.0 TOG) for warm nights, a midweight (1.5 TOG) for most of the year, and a heavier one (2.5 TOG) for cold nights. Pair them with short-sleeve and long-sleeve bodysuits, and you can cover nearly any temperature by mixing and matching.
Check the room thermometer at bedtime, pick the closest match from the layering guide, and do a neck check about 10 minutes after putting your baby down. After a few nights, you’ll develop a feel for what your baby needs in your specific home. Babies who sleep in rooms that fluctuate overnight (if the heat cycles off, for example) do better in a slightly warmer sleep sack with lighter clothing underneath, so you can easily add or remove the base layer without disturbing the sack.