The simplest rule for dressing a baby at night is one layer more than you’d wear to sleep comfortably in the same room. That means if you’d be fine in a t-shirt, your baby needs a onesie plus a light wearable blanket or sleep sack. The key is matching what your baby wears to the room temperature while keeping loose bedding out of the crib entirely.
Start With Room Temperature
The recommended nursery temperature for babies is between 68 and 72°F (20 to 22°C). This range keeps most infants comfortable without heavy layering and reduces the risk of overheating, which is a known risk factor for SIDS. A simple room thermometer near the crib gives you a reliable number to work with, since hallway thermostats don’t always reflect what’s happening in the nursery.
If your home runs warmer in summer or cooler in winter, adjust clothing rather than cranking the thermostat. Babies regulate temperature less efficiently than adults, so the clothing choices matter more than you might expect.
What to Put on Your Baby
For a room sitting at 68 to 72°F, a cotton onesie or footed pajamas under a lightweight sleep sack is the standard setup. In warmer rooms (above 75°F), a short-sleeve onesie alone or a onesie with a very thin sleep sack is enough. In cooler rooms (below 65°F), you can layer a long-sleeve bodysuit under footed pajamas and pair that with a warmer sleep sack.
Use lightweight, breathable fabrics like cotton or bamboo viscose. Bamboo is about 40 percent more absorbent than organic cotton, which means it wicks sweat faster and helps keep skin dry. Its natural fiber structure also allows more airflow than cotton, making it a good choice for babies who tend to sleep hot. Cotton remains a reliable, widely available option that breathes well in moderate temperatures.
Avoid fleece or polyester in warm rooms. These trap heat and don’t wick moisture effectively.
How TOG Ratings Work
TOG is a measure of thermal resistance, essentially how warm a sleep sack or wearable blanket will keep your baby. The higher the TOG number, the warmer the garment. Matching the right TOG to your room temperature takes most of the guesswork out of nighttime dressing.
- 0.2 TOG: Very lightweight, best for rooms between 75°F and 81°F
- 1.0 TOG: Light warmth, best for rooms between 68°F and 75°F
- 1.5 TOG: Moderate warmth, best for rooms between 64°F and 72°F
- 2.5 TOG: Heavier warmth, best for rooms between 61°F and 68°F
- 3.5 TOG: Warmest option, best for rooms below 61°F
When you use a higher-TOG sleep sack, reduce the layers underneath. A 2.5 TOG sack with a long-sleeve onesie underneath is plenty for a cool room. Pairing a heavy sleep sack with thick pajamas is a common mistake that leads to overheating.
No Loose Blankets, No Hats Indoors
The American Academy of Pediatrics is clear: keep loose blankets, pillows, stuffed toys, and bumpers out of the sleep space. A wearable blanket or sleep sack replaces a traditional blanket safely because it stays on the baby’s body and can’t cover the face.
Hats should not be worn indoors for sleep once you’re home from the hospital. A baby loses excess heat through the head, so covering it interferes with temperature regulation and increases overheating risk. Socks or footed pajamas are fine if your baby’s feet feel cold, but mittens and hats stay off at bedtime.
Swaddling and When to Stop
Swaddling works well for newborns who startle awake easily. A snug swaddle with arms wrapped counts as a layer, so you typically only need a onesie underneath in a room at 68 to 72°F. Muslin or cotton swaddles are best for breathability.
The moment your baby shows signs of rolling, swaddling needs to stop immediately. Increased kicking, twisting, or any attempt to flip from back to belly means the swaddle is now a safety risk. A swaddled baby who rolls onto their stomach can’t use their arms to reposition or clear their airway. Most babies hit this milestone between 2 and 4 months. Transition to a sleep sack with arms free at that point.
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. If the skin there feels hot or sweaty, they’re overdressed. Hands and feet tend to run cool on babies and aren’t reliable indicators of core body temperature.
Signs of overheating include flushed or red skin, damp hair, unusual fussiness, or a baby who seems sluggish and overly tired. In more serious cases, you might notice rapid breathing or clammy skin. Babies can overheat without visibly sweating, so touch-checking the neck or chest before you go to bed yourself is a good habit.
If your baby feels too warm, remove a layer or switch to a lower-TOG sleep sack. If they feel cool on the chest or neck (not just the hands), add a layer. You’ll likely need to adjust a few times before landing on the right combination for your home’s typical overnight temperature.
Quick Reference by Room Temperature
These combinations work as starting points. Adjust based on how your individual baby runs (some sleep warmer than others).
- Above 75°F: Short-sleeve onesie or just a diaper, with a 0.2 TOG sleep sack or none at all
- 70 to 75°F: Long-sleeve onesie or footed pajamas with a 1.0 TOG sleep sack
- 65 to 70°F: Long-sleeve onesie under footed pajamas, or a onesie with a 1.5 to 2.5 TOG sleep sack
- Below 65°F: Long-sleeve bodysuit under footed pajamas with a 2.5 to 3.5 TOG sleep sack
The pattern is simple: as the room gets cooler, either add a clothing layer under the sleep sack or move to a higher TOG rating. Avoid doing both at once unless the room is genuinely cold. One adjustment at a time, then check your baby’s neck after 20 minutes to see how they’re doing.