What Should a 3–6 Month Old Wear to Bed at 15°C?

Why 15°C requires a different conversation

15°C is below the 16–20°C sleep temperature range that Red Nose Australia identifies as appropriate for babies. The calculator's answer — 3.5 TOG bag with a long-sleeve bodysuit and footed sleepsuit — is correct as a layering answer, but it shouldn't be the first answer. The first question is whether the room can be warmed toward 18–20°C. A bedroom held at 18–20°C with a 2.5 TOG bag is a more comfortable and more manageable environment than a 15°C room with a 3.5 TOG bag, and it's the approach a child health nurse would recommend first.

If heating the room is practical — a reverse-cycle unit, an oil-column heater with a tip-over cutoff, or a panel heater — setting it to 18–20°C is the primary answer for a 15°C bedroom. The 3.5 TOG combination below is for when heating isn't available, isn't reliable, or isn't affordable for tonight.

If the room consistently sits at 15°C or below and neither heating nor relocating baby is practical, that's a conversation worth having with your child health nurse. The layering answer has a ceiling — and at 15°C, you're near it.

When heating isn't possible: the 3.5 TOG combination

If the room can't be warmed, a long-sleeve cotton or bamboo bodysuit as the base layer, a footed sleepsuit on top of that, and then a 3.5 TOG sleeping bag is the right combination. This is the ceiling for clothing-based warmth — avoid adding a beanie (Red Nose Australia is clear that baby's head should remain uncovered during sleep), loose blankets over the bag, or extra clothing layered on top of the bag. The 3.5 TOG combination IS the answer; stacking more on top doesn't materially improve warmth and introduces other risks.

Natural fibres — cotton, bamboo, merino — are the right choice at this temperature. The ergoPouch 3.5 TOG sleeping bag is the most widely available 3.5 TOG option in Australian stores. The Grobag Extra Warm 3.5 TOG is an alternative worth checking.

In Hobart, Launceston, and rural Tasmania more broadly, many heritage sandstone and double-brick homes have good thermal mass — they hold warmth during the day but release it steadily overnight. The catch is that they take time to warm up if the heating hasn't been running through the day. If you're using a portable heater in the bedroom, run it for 30–60 minutes before putting baby down so the walls have absorbed some warmth, not just the air.

Signs you've got it right (or wrong)

At 15°C, the concern is chilling rather than overheating. Check the chest and back of the neck — warm to the touch is the goal. A cool or cold chest at this temperature is a sign the layering isn't working; if it coincides with unsettled sleep or frequent waking in the early hours, the room temperature is likely the cause.

Overheating is still possible — particularly if a portable heater runs through the night and the room climbs from 15°C toward 20°C while baby is in the 3.5 TOG bag. If you've added heating, check the baby and the thermometer again about an hour after putting baby down. Damp hair around the hairline or flushed cheeks while the room is now 20°C means the bag is too warm for the current temperature. Having a 2.5 TOG bag on standby is worth it if your room temperature is variable.

When room temperature shifts overnight

In Hobart and Launceston winters, an unheated bedroom doesn't recover overnight — it tends to drift lower. A heritage stone or brick bedroom that starts at 15°C at 7pm can reach 12–13°C by 3am as overnight temperatures in the Derwent and Tamar valleys fall toward single figures. Unlike the shoulder-season overnight-drop story that applies in warmer parts of Australia, the Tasmanian winter pattern is consistent cold from bedtime to morning.

Checking the room thermometer at the first night feed tells you whether the room is holding or falling further. If it's tracking down toward 12°C, the layering combination is still appropriate, but warming the room before the next sleep is the right call rather than looking for more layers. If you don't have a thermometer, the chest check at each feed is your primary tool — it won't give you a number, but it tells you what you need to know.

Frequently asked questions

Try a different temperature or age

• What a 3–6 month old should wear at 16°C