In summer, most babies sleep comfortably in a single lightweight layer, such as a short-sleeve bodysuit, paired with a low-TOG sleep sack or nothing over it at all. The goal is to keep your baby’s room between 68 and 72°F (20 to 22°C) and avoid overdressing, since overheating is a known risk factor for SIDS. Getting the balance right is simpler than it sounds once you understand a few basics.
Start With the Room Temperature
The ideal nursery temperature is 68 to 72°F (20 to 22°C) year-round. In summer, that can be hard to maintain without air conditioning. If your home runs warmer, the clothing adjustments below will help, but it’s worth doing what you can to cool the room first. A fan is one of the most effective tools: a study published in the Archives of Pediatrics found that fan use during sleep was associated with a 72% reduction in SIDS risk, with an even greater protective effect in warmer rooms specifically. Point the fan toward the center of the room to circulate air rather than blowing directly on your baby.
If you have air conditioning, set it to the 68 to 72°F range and dress your baby accordingly. If you’re relying on fans and open windows, you’ll likely need to strip your baby down to fewer layers on hotter nights.
What to Dress Baby In at Each Temperature
The American Academy of Pediatrics advises dressing infants in no more than one layer beyond what an adult would find comfortable. That’s a useful mental shortcut, but here’s how it breaks down more specifically for summer nights.
68 to 72°F (20 to 22°C)
This is the sweet spot. A long-sleeve bodysuit or footed pajama with a 1.0 TOG sleep sack works well. If your baby tends to run warm, swap to a short-sleeve bodysuit underneath.
73 to 77°F (23 to 25°C)
Switch to a short-sleeve bodysuit with a lightweight sleep sack rated 0.5 to 1.0 TOG. At the higher end of this range, you can drop the sleep sack entirely and use just the bodysuit.
Above 77°F (above 25°C)
The Lullaby Trust, a UK safe-sleep charity, notes that in really hot weather it’s fine for a baby to sleep in just a short-sleeve vest or even just a diaper. If the room is above 80°F (27°C) and you can’t cool it down, a diaper alone is a safe choice. Adding any layers at this temperature risks overheating.
These are guidelines, not exact rules. Every baby’s metabolism is slightly different, and the material of each garment traps different amounts of heat. The key is checking your baby rather than relying on a chart alone.
Understanding TOG Ratings
TOG is a measure of thermal resistance, essentially how much warmth a fabric traps. The lower the number, the lighter and more breathable the garment. For summer, look for sleep sacks rated between 0.5 and 1.0 TOG. These are thin enough to prevent overheating while still giving your baby a consistent, wearable layer that replaces loose blankets (which aren’t safe in the crib).
A 0.2 TOG sack is the lightest option available and works well for the hottest nights when you still want something over a diaper. Anything above 1.0 TOG is designed for cooler conditions and should be put away for summer.
Best Fabrics for Summer Sleep
Not all lightweight clothing performs the same. Three fabrics stand out for warm-weather baby sleep:
- Cotton is highly breathable and absorbent, wicking sweat away from skin. It’s widely available and easy to wash. Standard cotton bodysuits and pajamas are a reliable default.
- Muslin is a loosely woven cotton that allows even more airflow than standard cotton. Muslin sleep sacks are popular for summer because the open weave lets heat escape quickly.
- Bamboo has natural temperature-regulating properties and strong moisture-wicking ability, keeping skin dry if your baby sweats overnight. It tends to feel silkier and slightly cooler to the touch than cotton.
Avoid polyester, fleece, and flannel for summer sleepwear. These trap heat and don’t breathe well, even in thin layers.
How to Tell If Your Baby Is Too Hot
Since every baby and every room is different, the most reliable approach is to check your baby directly. Place two fingers on the back of their neck or on their chest. If the skin feels hot or damp compared to your own, they’re overdressed or the room is too warm.
Other signs of overheating to watch for:
- Sweating, especially around the neck, back, and underarms
- Flushed or red skin
- Rapid breathing
- Heat rash (small red bumps, often in skin folds)
- Restless, disrupted sleep or unusual fussiness
- Unusual lethargy or quietness
Hands and feet aren’t good indicators. Babies commonly have cool extremities even when their core is perfectly warm or too warm. Always check the chest or back of the neck instead.
Common Summer Sleep Mistakes
The most frequent error is overdressing. Parents naturally worry about their baby being cold, but in summer the greater risk is overheating. If you’re comfortable in a t-shirt and shorts, your baby needs roughly the same level of coverage, plus one thin layer at most.
Another mistake is adding a hat indoors. Babies release excess heat through their heads, and covering it during sleep traps that heat. Hats should never be worn in the crib. Similarly, avoid swaddling with thick blankets in warm weather. If your newborn still needs a swaddle, choose a single-layer muslin or cotton wrap rather than a plush or double-layer version.
Finally, don’t assume air conditioning solves everything without checking. A room can feel cool near the thermostat but warmer near the crib, especially if the crib is near a window that gets afternoon sun. A simple room thermometer placed at crib level gives you the actual temperature where your baby sleeps.