Keeping babies cool in summer heat: practical guidance

0-12 months · Care · Reviewed 20 June 2026 · All articles

Hot summer weather is wonderful for many families, but very young babies have limited ability to regulate their own body temperature and can overheat quickly. Knowing the early warning signs of heat stress, having simple cooling strategies ready, and understanding when to call for help can make a significant difference to your baby's safety and comfort during warm spells.

Why babies struggle with heat regulation

Newborns and young infants have an immature thermoregulatory system. The area of the brain that controls body temperature, the hypothalamus, is still developing in the first months of life. This means babies cannot shiver effectively to warm up or sweat efficiently to cool down in the way that older children and adults can.

Babies also have a high surface area relative to their body weight. This sounds helpful for releasing heat, but it also means they absorb heat from a warm environment much faster than adults. Their skin is thinner, their sweat glands are less mature, and they rely almost entirely on the people caring for them to move them out of hot environments, remove excess clothing, and keep them hydrated.

Babies under three months are particularly vulnerable. Their temperature control is at its least reliable during this period, and parents often add extra layers out of a reflex to keep newborns warm. In hot weather this habit needs to be consciously adjusted. A good rule of thumb recommended by many paediatricians is to dress your baby in one fewer layer than you are wearing. If you are comfortable in a short-sleeved top, your baby may need only a vest.

Heat stress can develop quickly, particularly in cars, rooms without airflow, or during afternoon outdoor time when direct sun is strongest. Being aware of this vulnerability is the first step to preventing problems.

Recognising signs of heat stress

Heat stress exists on a spectrum. Mild overheating is very common and easy to correct. More serious heat illness requires prompt action. The key is checking your baby regularly and knowing what to look for.

Mild signs of overheating include flushed, red or damp skin, particularly around the face and neck. Your baby may seem unsettled, cry more than usual, or pull at their clothing. Their skin may feel warm to the touch on the chest, back or tummy. These signs usually resolve quickly once you move the baby to a cooler space and remove a layer of clothing.

Moderate signs to watch for include rapid breathing that seems out of proportion to any activity, a faster-than-usual heart rate, and a reduction in wet nappies. In hot weather you should expect your baby to produce roughly as many wet nappies as usual. If feeds are going well but nappies are noticeably less wet or darker in colour, your baby may not be getting enough fluid.

Fontanelle changes are worth knowing about. The soft spot on the top of your baby's head is called the anterior fontanelle. In a healthy, well-hydrated baby it should feel flat or very slightly soft. A sunken fontanelle is a sign of dehydration and warrants prompt medical attention. A bulging fontanelle can signal other problems and also needs urgent assessment.

Serious heat illness signs include a body temperature above 38 degrees Celsius in a baby under three months, or above 39 degrees in an older baby, alongside hot and dry skin (not sweating despite the heat), unusual lethargy, limpness, difficulty waking, or loss of consciousness. These are emergencies. Call the emergency services or take your baby to the nearest emergency department immediately.

Practical cooling strategies

Most overheating in babies can be prevented or reversed with straightforward steps. The goal is to reduce the ambient heat around your baby and help their body release warmth gently.

Clothing choices matter. Dress your baby in loose, lightweight, breathable fabrics. Natural fibres such as cotton and muslin allow more airflow than synthetic materials. A single-layer cotton vest or bodysuit is often sufficient in hot indoor temperatures. Avoid hats indoors; hats trap heat from the head, which is one of the main ways babies release body warmth.

Keep the room cool. The most effective approach is to prevent the room from heating up in the first place. Close curtains and blinds on south- or west-facing windows during the hottest part of the day, typically between 11am and 4pm. Open windows in the early morning and late evening when the outside air is cooler. Cross-ventilation works well: opening windows on opposite sides of the home creates a draught that lowers indoor temperature.

Fans can help but should not blow directly onto a baby. Position a fan in the room to circulate air rather than aiming it at the cot or changing mat. Some families place a shallow tray of iced water in front of a desk fan to further cool the air, though take care that neither the ice nor the water is within the baby's reach.

Lukewarm baths are an effective and gentle cooling method. The water should be comfortable to the inside of your wrist, neither cold nor warm. A short bath of five to ten minutes can lower your baby's surface temperature noticeably. Do not use cold water as sudden cooling can cause the blood vessels in the skin to constrict, which actually traps heat inside the body.

Damp cloths applied to the forehead, back of the neck, underarms, and insides of the wrists are another practical option when a bath is not convenient. Wring the cloth well so it is damp rather than wet, and use water at room temperature.

Timing outdoor activities can reduce heat exposure significantly. Early morning and late afternoon, after 5pm, are the safest windows for outdoor time in summer. During peak heat, keep babies indoors or in well-shaded spaces, and always use a sun canopy or parasol if you are using a pram or buggy. Check that the sun shade is not trapping hot air inside the pram; this can actually raise the temperature around the baby rather than cooling it.

Hydration in hot weather

Keeping your baby well hydrated is one of the most important protections against heat illness. How you do this depends on your baby's age and how they are fed.

Breastfed babies under six months do not need water or any other fluid supplement, even in very hot weather. Breast milk is approximately 88% water and naturally adjusts to meet your baby's hydration needs. The watery foremilk that comes at the start of each feed is particularly hydrating. In hot weather, offer the breast more frequently than usual. Your baby may take shorter, more frequent feeds as they prioritise the foremilk. This is normal and helpful. There is no need to limit these feeds or worry that your baby is overfeeding.

Formula-fed babies under six months should also not be given plain water as their primary hydration source. Formula provides complete nutrition and hydration at this age. You can offer small amounts of cooled, boiled water between feeds if your baby seems thirsty in very hot weather, but speak to your health visitor or midwife if you are unsure. Do not dilute formula to try to make it more hydrating; this reduces the calorie and nutrient content and can cause serious electrolyte imbalances.

Babies over six months who have started solid foods can be offered small sips of cool, previously boiled water from a cup alongside their usual milk feeds. As you introduce more solid foods, you can also offer fruits and vegetables with high water content, such as cucumber, melon, strawberries, and courgette. These contribute meaningfully to fluid intake and also provide vitamins and minerals.

Signs of good hydration include regular wet nappies (typically six or more in 24 hours for a young baby), pale or clear urine, moist lips and mouth, and a baby who is alert and responsive between feeds. If you are seeing fewer wet nappies than usual, or the urine appears darker or more concentrated, increase feed frequency and monitor closely.

Car safety in hot weather

A parked car is one of the most dangerous environments for a baby in hot weather. Car interiors can reach extreme temperatures very rapidly, even on moderately warm days and even with windows slightly open. On a 25-degree day, the inside of a parked car can rise above 45 degrees Celsius within 30 minutes. On a 30-degree day, temperatures inside a car can exceed 50 degrees within an hour. Babies and young children are at far greater risk than adults in these conditions because their core body temperature rises three to five times faster.

Never leave a baby or young child unattended in a parked car. This applies even for very short stops, and even in the shade. Shade shifts with the sun, and shaded areas provide only partial protection from the heat that builds inside the vehicle itself.

When travelling with a baby in the car, use window sun shades on the rear windows to reduce direct solar heating of the back seat area. Rear-facing infant car seats mean your baby is facing the back of the car, which can make it harder to see them at a glance. Use a mirror designed for rear-facing car seats so you can check on your baby while driving. Before setting off, check that the seat belt buckle and seat surfaces have not become hot from sitting in direct sun; metal buckles in particular can reach temperatures that cause burns on delicate skin.

On arrival at your destination, always check the back seat before locking the vehicle. Make a habit of placing something you need, such as your bag or phone, in the back seat so you have to open the door before you can leave. If you ever see a child alone in a hot car, call the emergency services immediately.

During long car journeys in summer, plan regular stops to get your baby out of the seat and into the shade. The seat itself can restrict airflow around your baby and contribute to overheating. Dress your baby in light layers that you can remove easily during a journey.

When to call a doctor or seek emergency help

Most episodes of mild overheating resolve quickly with simple cooling and extra feeds. However, there are clear situations where you should seek medical advice without delay, and others that are genuine emergencies.

Call your doctor or health visitor the same day if your baby has fewer wet nappies than usual for more than a few hours despite normal feeding, if they seem unusually drowsy or difficult to wake, if they are not feeding as well as usual and the heat may be a factor, or if you are concerned and unsure whether what you are seeing is normal.

Seek urgent care or go to the emergency department if your baby has a fever of 38 degrees Celsius or above and they are under three months old. For this age group, any fever is a reason for prompt medical assessment, regardless of the apparent cause. For babies over three months, a temperature above 39 degrees Celsius combined with signs of heat illness requires urgent attention.

Call the emergency services immediately if your baby is very limp or floppy, is unresponsive or difficult to rouse, has stopped producing wet nappies for six or more hours, has a sunken fontanelle, is breathing very rapidly or has laboured breathing, or has lost consciousness. These are signs of serious heat illness or severe dehydration and require emergency medical care.

When you call for help, let the call handler know the ambient temperature your baby has been in, how long they may have been overheated, their last feed time, and when they last had a wet nappy. This information helps the medical team prepare the right response.

Frequently asked questions

How do I know if my baby is too hot?

Signs your baby is too hot include flushed or red skin, sweating, rapid breathing, and feeling warm to the touch on their tummy or back. They may also be unusually irritable or lethargic. If their skin looks mottled, they stop producing wet nappies, or they seem very drowsy and hard to rouse, seek medical advice promptly.

Can I give water to a breastfed baby in hot weather?

Babies under six months who are exclusively breastfed do not need extra water, even in hot weather. Breast milk is approximately 88% water and provides all the hydration your baby needs. Offering water can reduce their intake of breast milk and the important nutrients it contains. Instead, feed more frequently so your baby can take in more of the watery foremilk that comes at the start of a feed.

What is a safe room temperature for a sleeping baby in summer?

The recommended safe sleep temperature for a baby's room is between 16 and 20 degrees Celsius. During a heatwave this can be difficult to maintain. Keep curtains or blinds closed during the day to block direct sunlight, use a fan to circulate air (but not pointed directly at the baby), and dress your baby in lightweight, loose cotton clothing or just a nappy if the room is very warm. Check your baby's temperature regularly by feeling their chest or back.

How quickly does a parked car heat up in summer?

A car interior can reach dangerous temperatures within minutes of being parked in direct sunlight. On a 25-degree day, the inside of a car can exceed 45 degrees within 30 minutes. On a 30-degree day, interior temperatures can rise above 50 degrees in under an hour. Babies and young children are especially vulnerable because their bodies heat up three to five times faster than adults. Never leave a baby alone in a parked car, even briefly, and always check the back seat before locking the vehicle.

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