How to Dress a Baby for Sleep in Winter (UK Guide)

The heating clicks on, the nights get colder, and suddenly you are standing over the cot wondering if your baby is warm enough. Knowing how to dress a baby for sleep in winter is mostly about one thing: dressing for the room, not for the weather outside. This guide shows you how to do that calmly, and how to check your baby in a few seconds.

Quick answer: how to dress a baby for sleep in winter

Aim for a room of 16 to 20°C and check it with a room thermometer.
Use a well-fitting baby sleep bag or a thin blanket tucked in no higher than the shoulders. No duvets, quilts or pillows.
Add or remove a light layer, such as a vest or sleepsuit, to match the room. Follow the sleep bag maker’s tog guide.
No hats, coats or outdoor clothes indoors.
Check the back of the neck or the chest. Warm is right. Hot or sweaty means take a layer off. Cool hands and feet are normal.

Why overheating matters more than the cold

It feels natural to wrap a baby up more when it is cold. But The Lullaby Trust and the NHS both point out that overheating is linked to a higher risk of sudden infant death syndrome (SIDS). A baby who is slightly cool will usually wake and let you know. A baby who is too hot may not. So the safest approach in winter is to keep things simple: a comfortable room, a sensible number of layers, and a quick check.

For the wider picture of room set-up, see our guide to the best sleep environment for babies and our safe sleep practices. You can find all our sleep guides on the baby sleep topic page.

Step 1: measure the room, do not guess

The Lullaby Trust recommends a room temperature of 16 to 20°C for sleep. Guessing is unreliable, especially in winter, when a radiator can make one room much warmer than the rest of the house. A simple room thermometer placed near the cot, but not next to a radiator or window, gives you a number to work with.

Most babies do not need the heating on all night. Adding a light layer usually works better.
If you do leave the heating on, keep it low, so the room stays no higher than about 20°C.
Keep the cot away from radiators, heaters, fires and direct sunlight.

Step 2: choose a sleep bag or a thin blanket

A baby sleep bag (also called a sleeping bag or sleep sack) is a popular choice because it cannot be kicked off or pulled over the face. If you use one, The Lullaby Trust suggests:

the right size for your baby’s weight, so it fits well around the neck and armholes and your baby cannot slip down inside;
no hood;
no weighted sleep bags or weighted blankets;
no extra duvet or quilt on top.

If you prefer blankets, use one or more thin, cellular blankets, tucked in firmly no higher than your baby’s shoulders, with their feet at the foot of the cot. Layered thin blankets are easier to adjust than one thick one.

If your baby is still swaddled, keep it light and stop as soon as they show signs of rolling. See when to stop swaddling.

Step 3: understand tog ratings (and why the charts differ)

Tog is a measure of how warm a fabric is. The higher the tog, the warmer the sleep bag. You will see many tog charts online, and they do not always agree. That is because they come from different brands, and fabric, fit and filling vary.

The Lullaby Trust does not publish a tog chart for this reason: products differ, layers underneath change the warmth, and every baby is different. The most reliable approach is:

follow the guide printed by the maker of your sleep bag;
match it to the reading on your room thermometer, not to the season;
then check your baby, and adjust the layer underneath if needed.

As a rough orientation, many UK makers suggest a 2.5 tog bag for a room in the usual 16 to 20°C range, and a higher tog only for colder rooms. Treat any chart as a starting point, not a rule.

Step 4: pick the layer underneath

Under the sleep bag or blanket, think in light layers you can add or take away:

Warmer room: a vest or a short-sleeved bodysuit may be enough.
Room in the middle of the range: a long-sleeved sleepsuit, or a vest plus a sleepsuit, depending on the maker’s guide.
Cooler room: add one light layer rather than switching to something much thicker.

Avoid fleecy sleepsuits under a warm sleep bag, and avoid hot water bottles and electric blankets in the cot. If your baby has dry winter skin, soft breathable cotton next to the skin can help; see baby dry skin in winter.

Step 5: the 10-second neck check

This is the step that matters most. Slip your fingers onto the back of your baby’s neck or their chest.

Warm and dry: about right.
Hot, damp or sweaty: take off a layer or use a lighter sleep bag.
Cool to the touch: add a light layer.

Hands and feet often feel cool, even when your baby is comfortable. That on its own is not a reason to add more layers.

Hats, coats and coming in from the cold

Babies lose heat through their heads, which helps them cool down. That is why they should not wear a hat to sleep indoors. When you come home from a walk or a car journey, take off hats, coats and snowsuits straight away, even if your baby has fallen asleep. Outdoor clothing is designed for outdoors, and it can make a baby too hot once inside.

If your baby is unwell

Winter colds are common. A baby with a cold or a temperature may feel warmer than usual. Do not add extra layers or bundle them up. Dress them for the room as normal, or with fewer layers if they feel hot, and keep checking. Our guides to caring for a sick baby at night and baby fever explain what to watch for.

When to talk to your doctor

Contact your GP or call NHS 111 if:

your baby is under 3 months and has a temperature of 38°C or higher;
your baby is 3 to 6 months and has a temperature of 39°C or higher;
your baby is often hot and sweaty at night, even with light layers in a cool room;
your baby is feeding less than usual, has fewer wet nappies, or seems unusually sleepy or floppy;
you are worried for any other reason.

Call 999 or go to A&E if your baby has blue, grey or very pale skin or lips, is struggling to breathe, is hard to wake, has a fit, or has a rash that does not fade when you press a glass against it.

Frequently asked questions

What tog sleeping bag should my baby use in winter?

Go by the room, not the month. Many makers suggest 2.5 tog for a room of about 16 to 20°C, but check the guide that comes with your sleep bag and then do the neck check.

Is 3.5 tog too warm for a baby?

It can be in a normally heated room. Higher tog bags are meant for colder rooms. If your baby feels hot or sweaty on the neck or chest, switch to a lower tog or remove a layer underneath.

My baby’s hands are cold at night. Are they too cold?

Not necessarily. Cool hands and feet are normal. Feel the back of the neck or the chest instead.

Should I leave the heating on all night for my baby?

Usually not. The Lullaby Trust says babies rarely need heating on all night. If you do use it, keep the room no warmer than about 20°C.

Can my baby wear a hat to sleep if the room is cold?

No. Babies should not wear hats to sleep indoors. Add a light layer under the sleep bag instead.

Sources

The Lullaby Trust: Room temperature and safer sleep
The Lullaby Trust: Safer sleep advice
NHS: Reduce the risk of sudden infant death syndrome (SIDS)
NHS: Fever in children
American Academy of Pediatrics: Safe sleep recommendations (2022)

This guide is general information, not medical advice. If you are worried about your baby’s health, temperature or breathing, talk to your pediatrician, or call 911 in an emergency.