A caregiver checking a plain room thermometer while a baby sleeps safely on their back in a clear cot

What temperature should a baby's room be?

It is 2am, the landing is cold, and the nursery thermometer says 21°C.

Aim for 16–20°C as a practical guide, where you can. That range comes from The Lullaby Trust's room-temperature guidance and NHS safer-sleep guidance, but it is not a magic number. Use it alongside two other checks: how your baby feels on the chest, back of the neck or tummy, and what your exact bedding or sleeping-bag instructions say for that room temperature.

A caregiver checking a plain room thermometer while a baby sleeps safely on their back in a clear cot
A room reading is a useful starting point; the cot setup and how your baby feels matter too.

Use the number as a guide, not a verdict

A room thermometer helps because room temperature is difficult to guess by feel, especially at night. Keep it near where your baby sleeps, away from a radiator or sunny window, so it reflects the sleep space rather than a warm corner.

There is no scientifically proven ideal for every baby. The Lullaby Trust's 2026 evidence review is clear that infant temperature regulation is still developing and research does not support one perfect room temperature for all infants. Think of 16–20°C as a starting point, then check your baby and adjust the layers.

So do not chase 18°C. You may see it called a "sweet spot" online, but that is shorthand, not a proven optimum. A degree above or below the guide matters far less than whether your baby feels comfortably warm, not hot, and whether the layers match the product you are actually using.

Check your baby, not just the display

The thermometer measures the room. Your hand tells you how your baby is coping with it.

Feel the chest, the back of the neck or the tummy. Warm, calm skin is reassuring. Cooler hands and feet on their own are common and are not a reliable reason to add another layer. If the skin on the chest or neck feels hot or sweaty, or the tummy feels hot rather than warm, remove a layer of bedding or clothing and check again shortly.

Other signs of being too warm include sweating and flushed or red cheeks. UK safer-sleep guidance links getting too hot with a higher risk of sudden infant death syndrome (SIDS), which is why it keeps returning to the same simple rule: comfortable, not too hot or too cold.

Make this your bedtime habit: glance at the thermometer, feel your baby, then adjust. The display informs you. Your baby decides.

A caregiver gently checking a baby's chest while the baby rests on their back in a clear cot and a room thermometer sits outside it
Check the chest, back of the neck or tummy as well as the room reading.

Why one chart cannot dress every baby

TOG, the warmth rating used for baby sleeping bags, sounds as if it should settle the question. Find the room temperature, read across, choose the TOG. In practice, it is not that neat.

The Lullaby Trust deliberately does not publish one universal temperature-to-clothing chart. Materials insulate differently, the air trapped between layers changes the warmth, and every baby is different. A cotton cellular blanket plus a vest is not the same as a padded sleeping bag with the same label, even at the same room temperature.

You can see the problem on ordinary retail pages. One UK sleepwear article says 16–20°C in the main text and 16–22°C in its own FAQ, with overlapping TOG bands around it. That gap is not a detail to split by averaging. It is the reason not to average charts at all.

Follow the instructions for your exact sleeping bag or swaddle, including what to put underneath it. The NHS gives 2.5 TOG for a standard 16–20°C room only as an example for well-fitting bags, not as a rule for every product. If you want more on layers, vests and fitting, our companion guide on how to dress your baby for sleep walks through it separately.

A plain room thermometer, cotton sleepsuit and fitted baby sleeping bag on a chest of drawers beside an empty clear cot
The room reading, the sleep space and the exact sleepwear instructions belong together.

If the room is warm or cold

Rooms move with the weather, and most nights do not sit neatly inside the guide. Adjust the layers and bedding first, rather than forcing the room to obey the thermometer.

If the room feels warm:

  • Dress your baby in lighter clothing and use lighter bedding or a lower warmth-rating bag, following that product's own instructions.
  • Keep the head uncovered. Babies do not need hats indoors for sleep.
  • If you open a door or window, do so only where it is safe, and keep the cot out of direct sunlight and direct draughts.
  • A fan can move air around a stuffy room. Do not aim it directly at your baby, keep cables well away from the sleep space, and let an adult handle setup.

If the room feels cool:

  • Add one light layer rather than piling on blankets. An extra vest layer under a well-fitting sleeping bag is often enough.
  • Heating left on all night is rarely needed. If you do leave it on, keep it low and no higher than 20°C, and keep the cot or Moses basket away from radiators, heaters and fires.
  • Use light bedding or a sleeping bag that fits snugly around the shoulders with no extra bedding needed. Follow the supplied user guide and any warnings for your exact product.
  • Never use a hot-water bottle or electric blanket to warm a baby's sleep space, and never place a bedside light under bedding or inside the cot.

Small, calm changes work best. Change one thing, feel the chest or neck again, and give it a little time before adding more.

Two baby sleepwear arrangements, lighter and warmer, laid out beside a plain room thermometer on a nursery changing table
When a room feels warmer or cooler, make one small layer change and check your baby again; this is not a universal TOG chart.

Simple safer-sleep checks around temperature

Temperature sits inside the wider sleep setup. These stay the same whatever the thermometer says:

  • Keep your baby's head uncovered during sleep. No hats indoors unless a doctor or midwife has advised them.
  • Use a firm, flat sleep surface with a clear cot. No duvets, quilts, pillows or loose bedding around a sleeping baby.
  • Place the cot away from radiators, heaters, fires and direct sunlight, and keep charging cables and power sources away from the sleeping area.

When it is not really about the room

Sometimes the worry is body temperature, not room temperature. The two need different responses.

A temperature of 38°C or more, measured with a thermometer, counts as a high temperature in a child. If a baby under 3 months reaches 38°C or higher, contact NHS 111 urgently. Do not wrap an unwell baby up more than usual, and ask your GP, health visitor or NHS 111 for advice when you are worried.

Tonight, keep the sequence simple: read the thermometer near the cot, feel the chest or back of the neck, match the layers to your exact product's instructions, and keep the head clear and heat sources at a distance.

Keep reading: for the 2am check itself, our guide to dream feeds and night checks without waking everyone covers seeing what you need to see in the dark, and what colour night light is best for babies explains why a dim, warm light is the gentler choice. You can also browse our nursery night lights.

References

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