The simplest rule for dressing your baby for sleep: one layer more than what you’d wear comfortably in the same room. That single guideline, recommended by the American Academy of Pediatrics, prevents both overheating and getting too cold. The details below will help you choose the right sleepwear for every temperature, pick the safest materials, and know exactly how to check whether your baby is comfortable.
Why Getting It Right Matters
Overheating during sleep is a known risk factor for Sudden Infant Death Syndrome (SIDS). Babies can overheat from too many layers, too-warm fabrics, or a room that’s too hot. Unlike older children and adults, infants can’t kick off blankets or tell you they’re uncomfortable, so the clothing choices you make before laying them down are their primary temperature protection.
Loose blankets, pillows, stuffed animals, and crib bumpers should stay out of the sleep space entirely. That means your baby’s sleepwear itself needs to do the job of keeping them warm, since a traditional blanket isn’t safe in the crib.
Set the Room Temperature First
Aim for a room temperature between 68°F and 72°F (20°C to 22°C). Getting this right makes your clothing choices much simpler. If the room runs consistently warm or cool, adjust layers accordingly rather than fighting the thermostat with extra clothing. A basic room thermometer near the crib takes the guesswork out of it.
What to Dress Your Baby In
Warm Rooms (75°F to 81°F)
A short-sleeve bodysuit is enough. In very hot weather, a diaper alone is perfectly fine. If you’re using a sleep sack, choose the thinnest option available (rated 0.2 TOG) and skip any additional clothing underneath, or dress in just a diaper beneath it.
Comfortable Rooms (68°F to 75°F)
A long-sleeve bodysuit or footed pajamas paired with a lightweight sleep sack (1.0 TOG) works well in this range. If you skip the sleep sack, footed pajamas on their own are usually sufficient. This is the range most nurseries fall into, so this combination will likely be your go-to.
Cool Rooms (61°F to 68°F)
Layer a long-sleeve bodysuit under footed pajamas, then add a warmer sleep sack (2.5 TOG). The bodysuit underneath adds insulation without adding bulk. If the room sits at the higher end of this range, you may be fine dropping the bodysuit layer.
Cold Rooms (Below 61°F)
Use your warmest sleep sack (3.5 TOG) over a long-sleeve bodysuit and footed pajamas. Add an extra layer of clothing rather than piling on a second sleep sack. Doubling up on sleep sacks traps air between the layers and can cause dangerous overheating, even if each individual sack feels thin.
Understanding TOG Ratings
TOG stands for Thermal Overall Grade. It’s a standardized measurement of how warm a garment is. The higher the number, the warmer the fabric. Most sleep sacks list a TOG rating on the packaging, which makes matching sleepwear to room temperature straightforward.
- 0.2 TOG: Very lightweight, for rooms 75°F to 81°F
- 1.0 TOG: Light, for rooms 68°F to 75°F
- 1.5 TOG: Medium, for rooms 64°F to 72°F
- 2.5 TOG: Warm, for rooms 61°F to 68°F
- 3.5 TOG: Warmest, for rooms below 61°F
One important caution: layering two 1.0 TOG sleep sacks does not simply equal 2.0 TOG. The trapped air between layers makes it significantly warmer than you’d expect, increasing the risk of overheating. Always use a single, appropriately rated sleep sack instead of doubling up.
Swaddling vs. Sleep Sacks
Swaddling works well for newborns because it calms their startle reflex, the involuntary arm-flinging that wakes them up. But swaddling has a hard expiration date: as soon as your baby shows any signs of rolling over, you need to stop. Babies typically start showing these signs between 2 and 6 months, though some begin as early as 8 weeks.
Watch for these cues during awake time: rolling to one side during play, pushing up on their hands during tummy time, lifting their legs and dropping them to the side, or regularly breaking free from the swaddle. Any of these signals means it’s time to transition to a sleep sack with arms free. A baby who rolls while swaddled with arms pinned is in a dangerous position.
Sleep sacks are the safest long-term option. They keep your baby warm like a blanket would, but they can’t ride up over the face or bunch around the head. They’re essentially wearable blankets with armholes, and they work from the newborn stage through toddlerhood.
Choosing the Right Fabric
Cotton is the most common choice for baby sleepwear. It’s soft, affordable, and breathable. The downside is that cotton absorbs moisture and holds it against the skin rather than pulling it away, which can leave your baby feeling clammy on warm or humid nights.
Bamboo fabric is roughly 20% more breathable than cotton of the same weight. It wicks sweat outward to the fabric’s surface where it evaporates, keeping skin drier. Testing shows bamboo viscose lowers skin surface temperature 2 to 3 degrees Celsius faster than cotton under the same conditions. For babies who tend to run hot or in warmer climates, bamboo sleepwear can make a noticeable difference.
Whichever fabric you choose, look for snug-fitting sleepwear. Loose, flowing garments are a fire hazard and can bunch up around the face. Most infant sleepwear is designed to fit close to the body for exactly this reason.
No Hats Indoors
Babies lose a significant amount of heat through their heads, which is exactly why hospitals put hats on newborns right after birth. But once you’re home, hats should come off for sleep. A hat prevents your baby from releasing excess heat and can contribute to overheating. If the room is cool enough that you’re tempted to add a hat, add a warmer layer of clothing to the body instead.
How to Check if Your Baby Is Comfortable
Don’t rely on your baby’s hands and feet to gauge temperature. They’re normally cooler than the rest of the body and will mislead you into thinking your baby is cold when they’re fine. Instead, place your hand on your baby’s chest or the back of their neck. The skin there should feel warm but not hot or damp.
Signs your baby is too warm include sweating (especially around the neck, back, and underarms), flushed skin, skin that feels noticeably hot compared to your own, rapid breathing, or unusual lethargy. If you notice any of these, remove a layer. Heat rash, which looks like tiny red bumps, is another indicator that your baby has been too warm.
Signs your baby is too cold are less common in a properly heated home, but include cool skin on the chest or belly, mottled skin color, and fussiness. Adding a single layer or increasing the TOG rating of the sleep sack typically solves the problem.
Weighted Sleep Products
Weighted swaddles, blankets, and sleep sacks are not recommended for babies under one year. They carry risks of overheating and can shift to cover the baby’s head. Despite marketing claims about improved sleep, major safe sleep organizations advise against them for infants.