The simplest rule for dressing your baby for sleep: one layer more than what you’d wear to be comfortable in the same room. That single guideline covers most situations, but the details matter because overdressing a baby carries real risks. Overheating during sleep is a known risk factor for SIDS, so getting the layers right isn’t just about comfort.
Start With the Room Temperature
Before choosing what your baby wears, check how warm the room is. Most sleep safety organizations recommend keeping the nursery between about 68°F and 72°F (20°C to 22°C). The AAP hasn’t set a single target number because overheating definitions vary across studies, but that range is widely used as a practical starting point.
If you don’t have a thermometer in the nursery, your own comfort is a reasonable gauge. If the room feels comfortable to you in a t-shirt, it’s likely in the right range. From there, dress your baby in one additional layer beyond what you’d choose for yourself.
What to Dress Baby in by Temperature
The specific combination of clothing depends on how warm or cool the room is. Here’s a practical breakdown:
- 75°F and above: A short-sleeve bodysuit (onesie) alone, or even just a diaper in very hot weather. If using a sleep sack, choose the thinnest option available (0.2 TOG).
- 68°F to 75°F: A long-sleeve bodysuit or footed pajamas, paired with a lightweight sleep sack (1.0 TOG). In the warmer end of this range, a short-sleeve bodysuit under a sleep sack works well.
- 64°F to 68°F: Footed pajamas with a mid-weight sleep sack (1.5 TOG), or a long-sleeve bodysuit layered under a warmer sleep sack (2.5 TOG).
- Below 64°F: A long-sleeve bodysuit under footed pajamas, plus a heavier sleep sack (2.5 or 3.5 TOG). Add a clothing layer rather than piling on extra blankets or doubling up sleep sacks.
Understanding TOG Ratings
TOG is a measure of thermal resistance, essentially how much warmth a fabric traps. Sleep sacks are rated by TOG so you can match them to your room temperature. Lower numbers mean thinner and cooler; higher numbers mean thicker and warmer.
A 0.2 TOG sleep sack is barely more than a single layer of cotton, good for warm rooms and summer nights. A 1.0 TOG is the most versatile year-round option for rooms kept around 68°F to 75°F. A 2.5 TOG is a winter-weight sack for cooler rooms. One important warning: don’t stack two sleep sacks thinking you’re adding the TOG values together. Air gets trapped between the layers and increases warmth unpredictably, which raises overheating risk.
Fabrics That Help Regulate Temperature
Cotton is the classic choice for baby sleepwear because it’s soft, breathable, and widely available. It works well for most situations. Bamboo viscose is another popular option that’s roughly 40% more absorbent than organic cotton and evaporates moisture faster. The natural pore structure of bamboo fibers allows more air circulation, which makes it a strong choice for babies who tend to sleep hot or sweat at night.
Avoid polyester and synthetic fleece for the layer closest to your baby’s skin. These fabrics trap heat and don’t wick moisture well, which makes overheating more likely. If you use a fleece sleep sack, keep the clothing underneath light.
How to Check if Your Baby Is Too Warm
Babies can’t tell you they’re overheating, so you need to check. Touch the back of your baby’s neck or place your hand on their chest. If the skin feels hot, damp, or sweaty, they’re overdressed. You can also feel their ears for a quick read.
Don’t rely on their hands and feet. Babies naturally have cooler extremities because of their developing circulation. Cold fingers don’t mean a cold baby. Signs of genuine overheating include flushed cheeks, rapid breathing, damp hair, and a sweaty chest or back. If you notice these, remove a layer and check again in 10 to 15 minutes.
Swaddling and When to Stop
For newborns who aren’t yet rolling, a snug swaddle can help with sleep. But you need to stop swaddling as soon as your baby shows any signs of trying to roll over. Some babies start working on rolling as early as 2 months, though every baby is different. This includes wearable swaddles or sleep sacks that compress the arms and chest.
Once you transition out of swaddling, move to an arms-free sleep sack. These let your baby move freely while still providing warmth without loose blankets in the crib. Most babies adjust to the switch within a few nights.
What Not to Put on a Sleeping Baby
A few items are specifically flagged as unsafe for infant sleep:
- Hats: Babies lose excess heat through their heads. Covering their head indoors blocks this natural cooling process and can cause overheating. The AAP recommends that infants not wear hats indoors except during the first hours after birth or in the NICU.
- Weighted sleep sacks and swaddles: These products have been linked to reduced oxygen levels in infants. The AAP and the Consumer Product Safety Commission both advise against placing weighted products on or near a sleeping baby. Several major retailers have pulled them from shelves.
- Loose blankets: No loose bedding of any kind in the crib for babies under 12 months. A folded blanket counts as two blankets’ worth of warmth, which is another reason sleep sacks are the safer alternative.
Summer and Winter Adjustments
In summer, the biggest risk is overdressing out of habit. If your home doesn’t have air conditioning and the nursery climbs above 75°F, strip down to a diaper and a single light layer, or just a diaper alone. A fan circulating air in the room can help, and studies have shown it may reduce SIDS risk independently.
In winter, resist the urge to pile on layers. If your home stays around 68°F, a footed onesie and a 1.0 to 1.5 TOG sleep sack is plenty. If the room drops below 64°F, add a bodysuit layer underneath the pajamas before reaching for a heavier sleep sack. The goal is to build warmth through thin, breathable layers rather than one thick, heavy covering.
Keep in mind that room temperature can shift overnight, especially in older homes. A simple room thermometer near the crib takes the guesswork out of it and costs just a few dollars.