The simplest rule for dressing your newborn at bedtime: one more layer than you’d wear to sleep comfortably in the same room. That single guideline covers most situations, but the details matter. Room temperature, fabric choice, and what counts as a safe “layer” all affect whether your baby sleeps safely and comfortably through the night.
Start With Room Temperature
The ideal nursery temperature falls between 68 and 72°F (20 to 22°C). This range keeps most newborns comfortable without heavy layering and reduces the risk of overheating, which is a known risk factor for SIDS. A simple indoor thermometer near the crib gives you a reliable read, since your own perception of the room can be thrown off by your activity level or clothing.
Once you know the room temperature, you can match your baby’s sleepwear to it using a system called TOG ratings.
What TOG Ratings Mean
TOG stands for Thermal Overall Grade. It measures how warm a garment or sleep sack is. The lower the number, the lighter and cooler the fabric. The higher the number, the more warmth it provides. Most sleep sacks and wearable blankets list their TOG rating on the packaging, making it easy to match sleepwear to your nursery conditions.
- 0.2 TOG: Best for warm rooms, 75°F to 81°F. A single lightweight layer underneath, or just a diaper.
- 1.0 TOG: Best for moderate rooms, 68°F to 75°F. A short-sleeve onesie or bodysuit underneath.
- 1.5 TOG: Best for slightly cool rooms, 64°F to 72°F. A long-sleeve onesie underneath.
- 2.5 TOG: Best for cool rooms, 61°F to 68°F. A long-sleeve onesie or footed pajamas underneath.
- 3.5 TOG: Best for cold rooms below 61°F. Footed pajamas with a long-sleeve layer underneath.
These are starting points. Babies vary in how warm they run, so you’ll still need to check your baby’s temperature after putting them down.
What to Actually Put On Your Baby
For the most common nursery temperature of around 70°F, a typical combination is a short-sleeve cotton onesie as a base layer plus a 1.0 TOG sleep sack over it. That’s it. Lightweight, breathable clothing like cotton onesies or footed pajamas forms the foundation of newborn sleepwear at nearly every temperature. In warmer months or warmer rooms, you might skip the base layer entirely and use just a light sleep sack over a diaper. In cooler rooms, swap to a long-sleeve bodysuit and a heavier sleep sack.
Footed pajamas are useful because they eliminate the need for socks, which can come loose in the crib. If you use footless pajamas, socks are fine as long as they fit snugly.
Swaddling vs. Sleep Sacks
For the first weeks of life, swaddling helps newborns stay warm and feel secure, which can reduce the startle reflex that wakes them. Swaddles wrap snugly around the torso and arms while leaving the hips loose enough for healthy leg movement. Always place a swaddled baby on their back.
The critical safety rule: stop swaddling the moment your baby shows any sign of trying to roll over. This typically happens between 2 and 6 months. Signs include rolling during playtime, pushing up on their hands during tummy time, lifting their legs and flopping them to the side, or breaking free of the swaddle. A baby who rolls onto their stomach while swaddled can’t use their arms to reposition, which creates a suffocation risk.
Once you transition out of a swaddle, sleep sacks (also called wearable blankets) take over. They provide warmth without the entrapment risk of loose blankets, and they work from infancy well into toddlerhood. The AAP specifically recommends wearable blankets over traditional blankets for keeping babies warm during sleep. Avoid weighted swaddles and weighted sleep sacks entirely. They place too much pressure on a baby’s chest and lungs.
Fabrics That Work Best
Cotton is the most common choice for baby sleepwear and works well in moderate temperatures. It’s soft, widely available, and breathable. Its main drawback is that it absorbs moisture and holds it against the skin rather than pulling it away, which can feel clammy in humid conditions or if your baby sweats.
Bamboo viscose is roughly 20% more breathable than cotton of the same weight and actively wicks moisture to the fabric’s surface, where it evaporates. Testing shows it reduces skin surface temperature 2 to 3 degrees Celsius faster than cotton. For babies who run warm or in summer months, bamboo sleepwear can make a noticeable difference.
Avoid polyester and other synthetic fabrics for sleep. They trap heat and don’t breathe well, increasing the chance of overheating and heat rash.
No Hats Indoors
Newborns often come home from the hospital wearing a hat, so many parents assume hats should stay on at bedtime. They shouldn’t. The NIH specifically advises keeping your baby’s head and face uncovered during sleep. Babies release excess heat through their heads, and a hat disrupts that process. Wearing hats indoors can cause overheating, and overheated babies face a higher risk of SIDS and heat-related illness.
Nothing Loose in the Crib
This is non-negotiable. No loose blankets, pillows, stuffed animals, crib bumpers, or any other soft items in the sleep space. These increase the risk of suffocation, entrapment, and strangulation. A firm, flat mattress with a fitted sheet and your baby in appropriate sleepwear is the complete setup. If the room feels too cold for just a sleep sack, add a clothing layer underneath rather than adding a blanket on top.
How to Tell If Your Baby Is Too Warm
The best spot to check is the back of your baby’s neck or their chest. These areas give a more accurate read than hands or feet, which tend to feel cool regardless. If the skin feels hot or damp to the touch, your baby is overdressed. Normal infant body temperature ranges from 97.7°F to 100.4°F (36.5°C to 38°C). Anything above that range may signal overheating.
Other signs to watch for: sweating around the neck, back, or underarms. Heat rash, which looks like tiny red bumps, especially in skin folds. Rapid breathing. Unusual fussiness or, on the other end, unusual lethargy and quietness. If you notice any of these, remove a layer and check again in 10 to 15 minutes.
Overheating is a more common problem than being too cold. Babies who are chilly will generally wake up and let you know. Babies who are overheating don’t always signal as clearly, which is why it’s worth erring slightly on the cooler side when you’re unsure.
Quick Reference by Temperature
- Above 75°F: Diaper only, or diaper plus a 0.2 TOG sleep sack.
- 70°F to 75°F: Short-sleeve onesie plus a 1.0 TOG sleep sack.
- 65°F to 70°F: Long-sleeve onesie plus a 1.0 to 1.5 TOG sleep sack.
- 61°F to 65°F: Footed pajamas plus a 2.5 TOG sleep sack.
- Below 61°F: Long-sleeve layer under footed pajamas, plus a 3.5 TOG sleep sack.
These combinations give you a starting framework. Check your baby’s chest or neck 15 to 20 minutes after putting them down and adjust from there. Within a few nights, you’ll have a reliable sense of what works for your nursery and your baby.