What Should a 3–6 Month Old Wear to Bed at 18°C?

Why this combination works at 18°C

18°C sits in the middle of the 2.5 TOG band, which covers rooms from 16°C to 20°C — the step up to a 3.5 TOG bag only comes below 16°C, and 21°C steps down to 1.0 TOG. What changes at 18°C is the base layer: at 16–17°C, the cool end of the band, a long-sleeve singlet goes under the long-sleeve bodysuit or footed pyjamas; from 18°C a plain singlet is enough under the bag. If the room cools another degree or two before dawn, it's still inside the 2.5 TOG band — a quick check of their back or tummy tells you whether the plain singlet is still doing the job, and on nights you know will settle at 16–17°C, the long-sleeve singlet is the warmer base for that range.

At 3–6 months, a baby's temperature regulation is still developing. A newborn needs much closer monitoring; by three months the system is more settled — but not as robust as a toddler who can shift position to regulate.

If your baby is around the 4–5 month mark and showing any signs of rolling — arching their back, getting a shoulder to the floor — the fitted sleeping bag is the right setup. A well-fitted bag moves with the baby rather than twisting or bunching. Wrapping should already have stopped by this age — at 3 months or at the first signs of rolling, whichever comes first — and a baby shouldn't be wrapped and in a sleeping bag at the same time.

Signs you've got it right (or wrong)

At 18°C, the more likely problem is underdressing rather than overdressing. Baby's back and tummy are the reliable check points — not the hands or feet, which run cool even in a well-dressed baby. What you're looking for: warm, dry skin. A cool back or tummy at 18°C means the room has cooled past what the current layers cover. If your baby is waking more frequently in the pre-dawn hours without a clear feeding pattern, check the temperature first — rooms that start at 18°C can drop to 15°C or below by 4am in unheated or poorly-insulated homes.

Overheating is less common at 18°C but not impossible. If the nape of the neck feels damp, or you notice flushed cheeks and rapid breathing, lighten the base for the next sleep — a single layer under the 2.5 TOG bag. The touch test takes about ten seconds and removes the guesswork.

Layering for 18°C in an Australian home

In practical terms: a singlet as the base layer, a long-sleeve bodysuit or footed pyjamas over that, then the 2.5 TOG sleeping bag. Cotton and bamboo breathe better than polyester at this temperature — worth checking the label if you're buying new. The ergoPouch 2.5 TOG sleeping bag, or a Bonds cotton footed sleepsuit paired with a Bubba Blue sleep bag are all standard options in Australian baby gear stores.

In Canberra and the ACT — where 18°C bedroom temperatures are common for much of the year outside summer — many parents run electric panel heaters or reverse-cycle on a timer that turns off after midnight. An 18°C bedtime reading in those homes often drops to 14–15°C by sunrise once the heating cycles off. Dressing for where the room ends up is easier than getting up at 3am to add a layer: if it reliably settles at 16–17°C, start with the long-sleeve singlet base; if it falls below 16°C, that's 3.5 TOG territory. If your home uses reverse-cycle set to hold 18°C overnight, the standard combination works as-is and you won't see much variation.

When room temperature shifts overnight

Canberra and nearby areas — the Snowy Mountains foothills, Goulburn, Yass — are known for overnight temperature swings that catch new parents out. A crisp autumn evening at 18°C can become a cold room by 4am, particularly in a brick or concrete slab home that releases its daytime warmth quickly once the temperature outside drops.

Checking the room thermometer when you do the first night feed tells you what your house does — most parents work this out in the first two weeks. A drop to 16–17°C stays inside the 2.5 TOG band — the long-sleeve singlet base is the adjustment there. If your home reliably drops below 16°C overnight and heating isn't practical, the room has left the 2.5 TOG band. At that point, stepping up to a 3.5 TOG bag — the next rating up — is a simpler fix than stacking extra layers.

Frequently asked questions

Try a different temperature or age

• What a 3–6 month old should wear at 19°C
• What room temperature is best for baby sleep in Australia?
• TOG rating chart: which TOG for which room temperature