How to Choose the Right TOG Sleep Sack for Summer Nights in the US

The Number on the Tag Actually Matters

Most parents spend a lot of energy picking the right crib, the right white noise machine, the right swaddle. The sleep sack often gets chosen by feel — literally. It seems thin, it seems breathable, it goes in the cart. But the number printed on that tag — the TOG rating — is the single most useful piece of information on the whole garment, and it’s worth understanding before summer arrives.

TOG stands for Thermal Overall Grade, an internationally recognized measurement of how much warmth a fabric provides. The higher the number, the more heat the garment retains. The lower the number, the lighter and cooler it sleeps. It has nothing to do with how soft the fabric feels or how heavy it seems in your hands — a bamboo sleep sack can feel feather-light and still carry a 1.0 TOG rating that’s completely wrong for a 78°F nursery in July.

The practical range for baby sleep sacks runs from about 0.5 TOG on the light end up to 3.5 TOG for the coldest rooms. For most US families navigating summer, only two numbers really matter: 0.5 TOG and, in some air-conditioned homes, 1.0 TOG.

What Room Temperature Actually Looks Like in Summer

Here’s where US geography makes this more complicated than a single chart can capture. A nursery in Phoenix in August is a fundamentally different environment than one in coastal Maine. Even within the same city, whether you have central air conditioning, a window unit, or no AC at all changes everything.

The guidance most pediatric sources point to is a nursery temperature between 68°F and 72°F (20–22°C) for safe infant sleep. The American Academy of Pediatrics recommends dressing babies in clothing appropriate for ambient temperatures rather than specifying a single number, and studies suggest that rooms above 72°F may be too warm for comfortable, safe sleep.

But in practice, summer nights in the US rarely cooperate. Homes without central AC in the South or Southwest can stay well above 75°F overnight. Even in climate-controlled homes, the nursery temperature can drift — afternoon sun heating a west-facing room, an AC unit that cycles off at 2am, or a thermostat set in the hallway that doesn’t reflect what’s actually happening in the crib corner.

This is why a dedicated room thermometer placed near the crib is genuinely useful, not just a nice extra. The thermostat down the hall may read 70°F while the nursery is running several degrees warmer. Once you know the actual temperature your baby is sleeping in, choosing the right TOG becomes straightforward.

For most US summer nights — with or without air conditioning — 0.5 TOG is the correct choice. If your nursery consistently holds below 72°F due to a reliable AC system, a 1.0 TOG works. But if temperatures fluctuate overnight, the safer move is to stick with 0.5 TOG and adjust the layer underneath rather than switching sacks mid-season.

Why Overheating Is the Risk That Drives All of This

Babies cannot regulate their own body temperature the way adults can. They rely entirely on their sleep environment — and what they’re wearing — to stay in a safe thermal range. Overheating has been identified as a risk factor in sleep-related infant deaths, which is why the AAP consistently flags it as something to actively avoid rather than just monitor passively.

A sleep sack does two jobs at once: it removes the need for loose blankets (which pose a suffocation risk in the crib), and it keeps your baby’s temperature steady through the night. Skipping the sleep sack altogether on hot nights isn’t the answer — the sack is part of a safe sleep setup. The solution is choosing the right TOG for the conditions.

One of the most common mistakes parents make is checking their baby’s hands or feet to gauge temperature. A baby’s circulation is still developing, so cool hands are normal and tell you nothing reliable about core temperature. Instead, feel the back of the neck or the chest. It should feel warm and dry. If it’s sweaty or damp, the baby is too hot and you need to remove a layer or lower the room temperature. If it feels cool to the touch, add a layer.

Fabric Matters as Much as the Number

Two sleep sacks can carry the same 0.5 TOG rating and perform very differently on a hot night, depending on what they’re made from. A polyester-based sack traps moisture against the skin. A bamboo or muslin sack wicks it away.

For summer specifically, bamboo-derived fabrics and muslin are the practical choice. Bamboo fabric regulates temperature naturally and moves moisture away from the skin, which prevents the clammy, uncomfortable feeling that can wake a baby at 3am. Cotton muslin, particularly in a loose weave, allows airflow in a way that tightly woven synthetics simply don’t.

Loulou Lollipop’s 0.5 TOG Muslin Sleep Bags are made from Tanboocel — a bamboo-cotton muslin that uses 99% less water in production than conventional cotton and is naturally temperature-regulating. The sleeveless design lets heat escape from the arms and shoulders (the areas where babies lose the most body heat), and the 2-way zipper opens from the bottom for diaper changes without fully waking the baby. The construction is also hip-healthy, with extra room at the bottom to support free leg movement. These sleep bags are CPSC, CPSIA, and ASTM certified, OEKO-TEX Standard 100 certified, and follow AAP safe sleep guidelines — details that matter when you’re choosing something your baby wears every night.

The sleeveless design is worth noting specifically for summer. Sacks with attached sleeves can cause overheating even at lower TOG ratings, because they limit the body’s ability to release heat through the arms.

Answering the Questions That Come Up Every Summer

Can I use a 1.0 TOG if my house is air-conditioned? Yes — if your nursery consistently stays below 72°F due to AC, a 1.0 TOG is appropriate. The key word is consistently. If the temperature fluctuates overnight, stick with 0.5 TOG and adjust the layer underneath instead of relying on the sack to do all the temperature work.

My baby runs hot. Should I skip the sleep sack? The recommendation from safe sleep guidelines is to keep the sleep sack and go lighter on the layer underneath, rather than removing the sack entirely. Sleep sacks replace loose blankets and are an important part of a safe sleep setup. A baby who runs warm in a 0.5 TOG sack over a diaper is in a better position than one sleeping under a loose blanket.

What about daytime naps when it’s especially hot? Yes, you can use a different TOG for naps than for overnight sleep, depending on the room temperature at that time of day. Afternoon naps in a sun-warmed room may call for the lightest option you have — even diaper-only under a 0.5 TOG sack. The TOG chart applies equally to naps and nighttime.

What if I don’t have air conditioning? Dress for the actual room temperature, not the season. In a room running above 75°F, a 0.5 TOG sack over a diaper or a single short-sleeve onesie is appropriate. A fan pointed at the wall (not directly at the baby) can help circulate air and bring the effective temperature down. Keep the crib away from direct sunlight and windows that get afternoon heat.

For parents who want to explore the full sleep collection — including 0.5, 1.0, and 2.5 TOG options — it’s worth knowing that TOG ratings are consistent across seasons. The same logic that makes 0.5 TOG right for a hot July night makes 2.5 TOG right for a cold February one. You’re not buying a different product for summer; you’re buying the right product for your room temperature, whatever that happens to be.