The safest way to dress a newborn for sleep is in one fitted layer plus a swaddle or sleep sack, with no loose blankets, hats, or extra bedding in the crib. The ideal nursery temperature is 68 to 72°F (20 to 22°C), and your baby’s clothing should match the warmth of the room so they stay comfortable without overheating.
The One-Layer Rule
A good starting point is to dress your baby in one more layer than you’d wear comfortably in the same room. In a nursery kept at 68 to 72°F, that typically means a cotton onesie or footed pajama underneath a swaddle or wearable blanket. If the room runs warmer, a short-sleeved bodysuit alone under a lightweight sleep sack may be enough. If it runs cooler, a long-sleeved onesie or footed sleeper gives extra warmth beneath the outer layer.
Loose blankets, pillows, stuffed animals, and crib bumpers should never be in the sleep space. A wearable blanket replaces a traditional blanket entirely, keeping your baby warm without the suffocation risk of loose fabric near their face.
Swaddles vs. Sleep Sacks
For the first weeks of life, a swaddle wrap is often the best option. Swaddles wrap snugly around your newborn and help prevent the startle reflex (the sudden arm-flinging motion that wakes babies up). A good swaddle should be snug around the arms and chest but loose enough around the hips that your baby can bend and kick their legs freely. Always place a swaddled baby on their back.
The critical rule: stop swaddling as soon as your baby shows any signs of rolling over. This can happen as early as 8 weeks, though it more commonly occurs between 2 and 6 months. Signs to watch for include pushing up during tummy time, lifting their legs and flopping them to the side, or escaping from the swaddle repeatedly. A swaddled baby who rolls onto their stomach can’t use their arms to reposition, which restricts breathing.
Once you stop swaddling, switch to a sleep sack. Sleep sacks are wearable blankets with armholes that allow full movement while keeping your baby at a consistent temperature. They’re considered one of the safest sleep options from about 8 weeks onward. Look for secure closures, no loose parts, zipper guards, tagless interiors, and a roomy bottom that lets hips move naturally. If the transition feels abrupt, products with slight arm resistance can ease the shift from swaddle to full freedom of movement.
Choosing the Right TOG Rating
TOG stands for Thermal Overall Grade, and it measures how much heat a fabric traps. The higher the TOG number, the warmer the sleep sack. Matching the TOG to your nursery temperature is the simplest way to avoid over- or under-dressing your baby.
- Over 80°F (27°C): 0.2 TOG, a very lightweight single layer. Your baby may only need a diaper underneath.
- 73 to 79°F (23 to 26°C): 0.5 TOG. A short-sleeved bodysuit underneath is usually enough.
- 68 to 73°F (21 to 23°C): 1.0 TOG. This is the sweet spot for most climate-controlled homes. Pair with a long-sleeved onesie or light pajamas.
- 61 to 68°F (16 to 20°C): 2.5 TOG. A warmer sleep sack paired with footed pajamas.
- Under 60°F (below 16°C): 3.5 TOG. The warmest option, for poorly heated rooms or very cold climates.
If you don’t have a TOG-rated sleep sack, use the feel of your baby’s skin as a guide (more on that below). A room thermometer in the nursery takes the guesswork out of choosing layers each night.
Which Fabrics Work Best
Cotton is the classic choice for baby sleepwear because it’s soft, breathable, and easy to wash. It works well in moderate temperatures and is widely available in every style from onesies to footed pajamas.
Bamboo viscose has some advantages worth knowing about. The fibers are naturally hollow with microscopic gaps that wick moisture from skin up to four times faster than cotton and absorb roughly 40% more moisture by weight. That structure also helps regulate temperature in both directions: releasing heat when your baby is warm and retaining it when temperatures drop. If your baby tends to run hot or sweaty, bamboo is a strong option.
Fleece is best reserved for cold conditions and used carefully. It works by trapping air between fibers for insulation, but it doesn’t breathe well. Polyester fleece in particular can trap heat and moisture quickly, raising the risk of overheating in a heated indoor environment. If you use a fleece sleep sack, dress your baby in lighter layers underneath and monitor their temperature closely.
How to Check if Your Baby Is Too Warm
Newborns can’t regulate their own body temperature the way adults can, and overheating is a known risk factor for sleep-related problems. The most reliable check is to touch the back of your baby’s neck or their chest. These areas give you a better read on core temperature than hands or feet, which tend to feel cool even when a baby is perfectly comfortable.
Signs your baby is too warm include:
- Skin that feels hot to the touch, with or without a fever
- Flushed or red face
- Sweating or damp hair
- Fussiness or restlessness that doesn’t have another obvious cause
- Unusual sleepiness or listlessness
Heat rash is another telltale sign. It appears as tiny red bumps in your baby’s skin folds, around the neck, and on their bottom. If you see it regularly, your baby is consistently overdressed or the room is too warm. In more serious cases, overheating can cause a rapid or weak pulse and skin that feels clammy. If your baby seems confused, weak, or is vomiting, that signals heat exhaustion and needs immediate attention.
A baby who feels cool to the touch on the chest or whose lips look slightly blue is underdressed. Add a layer or increase the TOG rating of their sleep sack.
What Not to Put on a Sleeping Baby
Hats should come off for sleep. Babies release excess heat through their heads, and a hat can cause them to overheat without you realizing it. Mittens are fine for preventing scratching during the day, but for sleep they add unnecessary warmth and can come loose in the crib. Socks under footed pajamas double up insulation on the feet and can also come off and become a loose item in the sleep space.
Avoid any sleepwear with hoods, drawstrings, ties, or decorative elements that could come loose. Zippers are generally safer than snaps because they stay flat and secure. Two-way zippers that open from the bottom make middle-of-the-night diaper changes easier without fully undressing your baby or waking them up more than necessary.
Putting It All Together
For a room at 70°F, a typical setup looks like this: a long-sleeved cotton or bamboo onesie, a 1.0 TOG sleep sack, and nothing else in the crib. If your newborn is under 8 weeks and not yet rolling, you can substitute the sleep sack for a swaddle of similar warmth. Check the back of their neck after 20 minutes to make sure they’re not too hot or too cold, and adjust from there.
Babies’ temperature needs can shift from night to night depending on whether they’re fighting a cold, how warm the room gets overnight, or even how recently they ate. Getting the layers right isn’t a one-time decision. It’s a quick nightly habit: check the room temperature, pick the right TOG, choose the base layer, and do a skin check before you go to bed yourself.