What Should a 3–6 Month Old Wear to Bed at 20°C?

What makes 20°C a boundary temperature

20°C is the warmest temperature in the 2.5 TOG band — one degree warmer and the recommendation steps down to a 1.0 TOG sleeping bag. Unlike the cooler end of this band (18–19°C), where the main concern is whether the room might drift colder overnight, at 20°C the concern runs the other way: if the room warms above 21°C, the 2.5 TOG bag starts becoming too much. The bag is working at its upper limit at 20°C, not in the comfortable middle of its range.

For a 3–6 month old, the combination is a long-sleeve bodysuit under a 2.5 TOG sleeping bag. A long-sleeve bodysuit is appropriate for a room that holds steadily at 20°C overnight. If the room frequently edges above 21°C — common in early summer — switching to a short-sleeve bodysuit or dropping to the 1.0 TOG bag becomes the more accurate response rather than adjusting the layer underneath.

The rolling note applies at this age: by 4–5 months, many babies show rolling signs, and the fitted sleeping bag matters more than a swaddle for safety. An arms-free swaddle is still appropriate at 20°C if baby has no rolling signs — at this temperature the warmth difference between a swaddle and the 2.5 TOG bag is less critical than in colder rooms. Once any rolling begins, the fitted bag is the right call.

Signs you've got it right (or wrong)

At 20°C, overheating is a more common concern than at 18–19°C — the room is at the warm end of the 2.5 TOG range, and any upward drift pushes toward 1.0 TOG territory. Check the chest and back of the neck: warm but not damp is the goal. Damp hair around the hairline, flushed cheeks, or rapid breathing — particularly if you notice them later in the night when the room may have warmed — signal that the 2.5 TOG bag is running heavy.

If the touch check feels borderline, check the room thermometer at the same time. A room that reads 21°C or above is the culprit, not the layering itself. Adjust the bag on the next sleep rather than adding or removing base layers — the 1.0 TOG bag is designed for 21–23°C and is the cleaner solution than trying to compensate with a short-sleeve bodysuit under a 2.5 TOG bag.

Layering for 20°C in an Australian home

In concrete terms: a long-sleeve cotton bodysuit under a 2.5 TOG sleeping bag. The ergoPouch 2.5 TOG sleeping bag or cocoon, the Love to Dream Swaddle UP 2.5 TOG, or a Bonds cotton bodysuit paired with a Bubba Blue 2.5 TOG bag are standard options in Australian stores. Cotton and bamboo breathe better than polyester at the warm end of this temperature range.

Along the Wollongong and Illawarra coastline, autumn and spring evenings regularly sit at 18–21°C and hold remarkably steady overnight, moderated by the Tasman sea breeze that runs against the escarpment. A 20°C bedtime reading in Corrimal, Wollongong, or Figtree in April or September typically means a 19–21°C room by midnight — stable enough that the 2.5 TOG combination works through to morning without adjustment and without the overnight-drop anxiety that applies in drier, more continental parts of the country.

When room temperature shifts overnight

Coastal stability has a seasonal limit. In October and November, as summer approaches on the NSW south coast, a 20°C Wollongong bedroom at bedtime can warm toward 22–23°C by midnight as the day's heat builds in the house before the overnight sea breeze strengthens. At 22°C the 2.5 TOG bag is running noticeably heavy — that's the territory where the 1.0 TOG recommendation applies.

Checking the room thermometer at the first night feed in October and November confirms what the season is doing to overnight temperatures. If the room has settled above 21°C, switching to a 1.0 TOG bag for the following night is the right call. The transition is clean: same bodysuit underneath, just the lighter bag. You don't need to change the whole layering system — just the bag.

Frequently asked questions

Try a different temperature or age

• What a 3–6 month old should wear at 19°C