Aim for a room of 16 to 20°C

The Lullaby Trust recommends a room temperature of 16 to 20°C for babies. A cheap room thermometer takes the guesswork out of it. If a room is slightly colder than that, its cold weather advice is to consider an extra lightweight blanket or layer of clothing, but not to overwrap. Warmer is not automatically safer: the NHS notes that overheating a baby increases the chances of SIDS.

The layers rule of thumb

NHS Best Start in Life's handy rule is to give your baby one extra layer of clothing than you're wearing. The Lullaby Trust warns that air gets trapped between layers and increases warmth, so piling things on adds up faster than you'd think, and two sleeping bags should never be used together.

Sleeping bags and TOG

TOG is simply how warm a product is: the higher the number, the warmer it is. The Lullaby Trust explains that every product and every baby is different, so there's no single chart that suits all, so follow the guidance for your particular bag. As a guide to what goes underneath, it suggests:

• Below 16°C: a baby grow with a higher TOG sleeping bag
• 16 to 20°C: a baby grow with a sleeping bag
• Above 20°C: a short-sleeved bodysuit or just a nappy

If you use blankets instead, the NHS recommends lightweight cellular ones rather than thick or fleecy ones, and reminds you that a folded blanket counts as two. The Lullaby Trust adds that they should be firmly tucked in, no higher than your baby's shoulders.

No hats indoors or for sleep

Hats are for outside. Babies release heat through their heads, so the Lullaby Trust says they don't need hats indoors, and a covered head during sleep can lead to overheating. Great Auntie Jean's knitted bonnet is for pram walks only.

Car seats: coats off

The Lullaby Trust's car seat advice is to remove hats and outdoor clothing, such as snowsuits and coats, once your baby is in the car, and to check they aren't getting too hot by feeling their tummy or the back of their neck. If the car is chilly while it warms up, a blanket over the top of the fastened harness can come off as soon as the heater kicks in. Car seats also aren't designed for sleep, so take regular breaks on longer journeys.

Pram walks and the big shop

For a crisp autumn walk, a pramsuit, a hat and a cellular blanket in the pram will usually see you through. The tricky bit is coming back inside. The NHS says to remove hats and extra clothing as soon as you're indoors or get into a warm car, bus or train, even if it means waking your baby. Shops in October are basically saunas with a meal deal, so unzip on the way through the door.

Signs your baby is too warm

Sweaty skin, a hot chest or tummy, or damp hair are all cues to take something off. And if your baby is unwell, the Lullaby Trust says not to be tempted to wrap them up more than usual. The NHS fever guidance agrees: don't cover a child with a high temperature in too many clothes or bedclothes, and don't undress or sponge them down either.

When to get help

A temperature in a young baby always needs a call. The NHS says to ask for an urgent GP appointment or call 111 if your baby is under 3 months old and has a temperature of 38°C or higher, or you think they have a high temperature, and its guide to whether your baby is seriously ill treats it as an emergency, so don't wait to see if it passes. Call 999 or go to A&E if your baby:

• is floppy, difficult to wake or cannot be woken
• has a very low temperature (below 36°C), feels cold to touch or is shivery
• has skin that feels cold or clammy, or skin, lips or tongue that look blue, grey, pale or blotchy

If you're unsure, call 111, your GP or your health visitor. You don't need to be certain to ask.

Stocking up for the season? Our autumn essentials for newborns covers the kit worth buying, and what TOG actually means goes deeper on sleeping bags once the clocks go back.

This is general information, not medical advice. You know your baby best, so trust your instincts, and if you're worried contact NHS 111, your GP or your health visitor (or 999 in an emergency). For the full guidance on keeping babies at the right temperature, see the Lullaby Trust's page on room temperature.