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The AC Is Running — So Why Is Your Baby Still Too Warm?
Summer in the US looks different depending on where you live. In Phoenix, the AC runs 24 hours a day and the nursery might hold steady at 68°F all night. In a Brooklyn apartment, the window unit struggles after midnight and the room climbs back to 76°F by 3 a.m. In a Houston suburb, the house stays cool but the humidity sneaks in anyway.
This is the part most TOG guides skip: your air conditioning does not guarantee a stable nursery temperature. It creates a range. And that range is exactly what determines which TOG sleep sack your baby needs this summer.
The short answer: for most air-conditioned nurseries in summer 2026, you’re choosing between a 0.5 TOG and a 1.0 TOG sleep sack. The longer answer is that the right choice depends on how consistently your AC holds the room below 72°F — and whether your baby tends to run warm.
TOG Ratings, Briefly Explained
TOG stands for Thermal Overall Grade — a textile industry measurement of how much heat a fabric retains. The higher the number, the more insulating the garment. A 2.5 TOG is built for cold winter rooms. A 0.5 TOG is built for warm nights. It’s a measure of insulation, not weight or thickness, which is why a thin TENCEL™ fabric can perform very differently from a thin cotton one.
The scale parents typically work with runs from 0.5 to 3.5. Most US families find they need two or three TOG ratings across the year: a lighter option for warm months, a mid-weight for shoulder seasons, and a heavier one for winter. Summer — especially in an AC’d nursery — sits firmly in the 0.5–1.0 range.
One thing worth knowing: TOG ratings are only one variable. The base layer underneath the sleep sack, the fabric type, and the actual room temperature all factor into how warm your baby sleeps. A 1.0 TOG in breathable TENCEL™ Lyocell behaves differently than a 1.0 TOG in a synthetic fleece — the former allows heat to escape; the latter tends to trap it.
The 0.5 vs 1.0 TOG Decision for an AC Room
Here’s where parents get stuck: the AC is on, so the room feels cool, but is it cool enough for a 1.0 TOG? The answer depends on a specific temperature threshold.
If your nursery consistently stays below 72°F (22°C) overnight, a 1.0 TOG sleep sack is appropriate — pair it with a short-sleeve bodysuit underneath and you’re in good shape. If the temperature fluctuates and climbs above 72°F at any point in the night, a 0.5 TOG is the safer call, and you can adjust warmth by changing the layer underneath rather than switching the sack itself.
Families in warmer climates like Florida, Texas, and Arizona often run their AC hard enough that the nursery holds at 68°F year-round. In those cases, a 1.0 TOG sleep sack works for most of the year — including summer. But in older homes, apartments with less efficient cooling, or rooms that face west and absorb afternoon heat, the temperature can swing 6–8 degrees between 9 p.m. and 4 a.m. That swing matters.
The practical rule: dress for the warmest point in the night, not the coolest. If the room peaks at 74°F at any point, reach for the 0.5 TOG. You can always add a light long-sleeve layer if the room gets colder than expected — but you can’t easily cool a baby who’s been overdressed for hours.
And if your baby runs warm in general — sweaty neck, flushed cheeks, restless sleep — lean toward the lower TOG regardless of what the thermostat says. Babies can’t regulate their own body temperature the way adults can, which means they rely entirely on their sleep environment and what they’re wearing to stay comfortable through the night.
Why Fabric Type Matters as Much as the TOG Number
Two sleep sacks can share the same TOG rating and perform very differently depending on what they’re made of. This is especially relevant in summer, when the difference between a breathable fabric and a heat-trapping one shows up in how your baby actually sleeps.
TENCEL™ Lyocell — the material used in Loulou Lollipop’s sleep bags — is derived from sustainably sourced eucalyptus tree pulp. Its fiber structure allows air to circulate freely while actively wicking moisture away from the skin, which helps maintain a balanced temperature even when the room warms slightly overnight. Unlike cotton, which absorbs sweat and stays damp, or synthetic fabrics that block airflow, TENCEL™ keeps the skin drier and cooler through the night.
This is why the fabric choice becomes particularly relevant for summer sleep. A 1.0 TOG in TENCEL™ Lyocell gives you a wider margin of comfort than a 1.0 TOG in polyester fleece — the breathability of the material effectively extends the temperature range it works well in. Loulou Lollipop’s TENCEL™ 1.0 TOG sleep bags are made from a blend of TENCEL™ Lyocell and organic cotton, manufactured at an OEKO-TEX Standard 100 certified factory — meaning no toxic chemicals, and a fabric that’s gentle enough for newborn skin.
For the warmest summer nights or rooms that sit consistently above 72°F, the 0.5 TOG muslin sleep bag is the lightest option — sleeveless, soft, and designed specifically for warm-weather sleep. The sleeveless construction is intentional: arms and shoulders are where babies lose the most body heat, so leaving them uncovered helps regulate temperature naturally.
How to Check If Your Baby Is the Right Temperature
The thermostat is a useful reference point, but it’s not the whole picture. Nursery thermometers can read differently depending on where they sit in the room, and a thermostat in the hallway tells you almost nothing about what’s happening near the crib.
The most reliable check is physical: feel the back of your baby’s neck or their chest — not their hands or feet, which naturally run cooler due to developing circulation. The skin there should feel warm and dry. If it’s sweaty or hot to the touch, they’re overdressed. If it feels cool or clammy, add a layer.
A few other signs to watch for: a flushed face, faster breathing, or restless, fragmented sleep can all indicate your baby is too warm. On the other side, if your baby wakes frequently and seems unsettled without obvious cause, a slightly cooler room or lighter sack might be worth trying.
One last thing worth noting: check the room temperature at bedtime, not based on the weather forecast. A cool afternoon doesn’t mean the nursery will stay cool at midnight, especially if the AC cycles off or the room holds residual heat from the day.
The Layering System That Makes One Sleep Sack Go Further
You don’t necessarily need a different sleep sack for every temperature variation. What changes more often is what goes underneath.
For a room running at 68–72°F, a 1.0 TOG over a short-sleeve onesie is a solid starting point. Drop the room to 65°F and you might add a long-sleeve bodysuit underneath the same sack. Push the room to 74°F and the 0.5 TOG with just a diaper or a thin onesie underneath is probably more appropriate.
The base layer does real work here. Adding a thin cotton bodysuit under a sleep sack is roughly equivalent to adding 0.5 to the insulation level — which means a single sleep sack can cover a wider temperature range than the TOG number alone suggests, as long as you’re adjusting the layer beneath it.
For parents who want one option that handles most summer scenarios in an AC room, the 1.0 TOG in TENCEL™ tends to be the most versatile pick. It works at 68–72°F with a short-sleeve layer, and if the room gets unexpectedly warm, the breathability of the fabric provides some buffer. Loulou Lollipop’s sleep bag collection covers 0.5 TOG through 2.5 TOG, so there’s an option whether your nursery runs cool and consistent or warm and variable.
And regardless of which TOG you choose: sleep sacks replace loose blankets, which is an important safe sleep consideration for babies under 12 months. The sack stays on, the temperature stays managed, and everyone gets more sleep — which is the actual goal.