Baby Won't Sleep in Hot Weather

Start with the room

The Lullaby Trust's hot weather guidance is a list of room measures rather than baby measures, which is the right order. Use lighter bedding and clothing with fewer layers. Open the bedroom door and a window, if it is safe to do so, to let air flow. Use a fan to cool the room, but do not aim it directly at your baby. Keep curtains closed in the daytime so the room does not heat up as much. And use a thermometer to check the room, because it is hard to guess.

The NHS heatwave advice for households points the same way and adds the timing: close windows, curtains and blinds during the day and open them at night when the temperature outside has dropped. It also notes that electric fans can help if the temperature is below 35C, and it lists babies and young children aged five and under among those most at risk in a heatwave.

When the room will not cool

The Lullaby Trust acknowledges this directly: you may find that even after doing all of the above, you still cannot get the room between 16 and 20C when it is particularly hot outside, and that this is frustrating. Its answer is to change what your baby wears rather than to abandon the rest of the advice. "In really hot weather, it's fine to have your baby in a short sleeve vest or even just a nappy."

Its published dressing guide for a room above 20C is the same: a lightweight layer such as a short-sleeved bodysuit, or just a nappy. No sleeping bag on top of that, no blanket, and no doubling of layers. The Lullaby Trust warns that one blanket doubled over counts as two, and that two 1.0 tog sleeping bags do not equal one 2.0 tog bag, because air trapped between layers increases warmth.

Checking your baby, not the thermostat

Feel your baby's chest or the back of their neck. Their hands and feet will usually feel cooler, which is normal. If their skin is hot or sweaty, they are too hot, and the answer is to remove one or more layers. The Lullaby Trust says research shows babies are safer being cooler than being too hot, because overheating raises the risk of SIDS.

Where the UK and Australia disagree

Two credible bodies take genuinely different positions here, and they should not be blended.

The Lullaby Trust names a range and asks you to measure it: 16 to 20C, checked with a room thermometer, because the risk of SIDS is higher in babies who get too hot.

Red Nose Australia declines to name one. Its position is that "there is no perfect temperature, and what is a safe temperature depends on many factors, including the season or how baby is dressed", and it goes further on the equipment: "To date, there is no evidence showing that a specific room temperature prevents sudden unexpected death in infancy." Red Nose puts the protective weight on three things instead — keep the head and face uncovered, place baby on their back, and dress them for the conditions, as you would dress yourself, comfortably warm.

They agree on the outcome. Both say overheating is a real risk, both say to check the baby rather than your own hands, and both say to strip layers when the baby feels hot. They disagree about whether a number and a thermometer are useful. If you live in the UK or Ireland you will be given the Lullaby Trust figure by your health visitor; if you live in Australia you will not be given a figure at all.

Fluids in the heat

The Lullaby Trust's hot weather guidance is specific. If you are exclusively breastfeeding, your baby does not need any extra water until they start eating solid food, but in hot weather they may want to breastfeed more often than usual. Once they are on solids they will need extra water. If you formula feed, you can offer a little cooled boiled water in addition to their usual milk feeds, and if they wake at night they will probably want milk.

Red Nose Australia's summer guidance agrees on the direction: breastfed babies may want to feed more often, formula-fed babies may need additional bottles, and hydration helps regulate body temperature.

What does not change because it is hot

Everything else. On the back, for every sleep, day and night. Own clear, flat, firm sleep space, in your room for at least the first six months. Cot kept away from radiators, direct sunlight and blind cords. Head and face uncovered, hats off indoors.

Two heat-specific traps are worth naming. Never cover a pram, buggy or travel system with a blanket, muslin or cover that stops air flowing — the Lullaby Trust recommends a clip-on sunshade or parasol instead, so air circulates and you can see your baby. And do not let a hot night become the night you move your baby somewhere cooler that is not a safe sleep space, such as downstairs on a sofa with you.

When to ask

Get advice if your baby is drowsy or floppy, is feeding much less than usual, has had no wet nappy for 12 hours or more, has hot dry skin, is unusually irritable, or has a temperature of 38C or above under three months. Call 999 if your baby is very hard to wake, is limp, or has blue, grey or very pale skin.