Short answer: Babies can overheat more easily than adults, and overheating is a risk factor for sudden infant death. In hot weather, keep the room as cool as you can (ideally 16–20 °C for sleep), dress your baby in fewer layers, offer more breast or formula feeds, keep babies under six months out of direct sun, and never cover a pram or pushchair with a blanket or cloth. Check your baby's temperature by feeling their chest or the back of their neck. Get medical advice for signs of overheating or dehydration.
It's 30 °C, and you have a baby who can't tell you they're too hot, can't get a drink when they want one and can't kick off a blanket.
Why heat is different for babies
Young babies are less able to regulate their temperature, and the NHS lists babies and children under five among the groups most at risk in a heatwave. Overheating is also a known risk factor for sudden infant death syndrome (SIDS), so getting sleep right matters.
Sleeping in hot weather
- Check your baby's temperature by feeling their chest or the back of their neck. Hands and feet usually feel cooler and aren't a good guide.
- Room temperature: the Lullaby Trust recommends 16–20 °C for sleep. In a heatwave this can be hard; do what you can and dress your baby accordingly.
- Fewer layers: in very hot weather, a nappy and a vest, or just a nappy, may be enough. Use a lighter sleeping bag (lower tog) or a single thin sheet tucked in no higher than the shoulders.
- Keep the room cool: close curtains and blinds during the day, and open windows when it's cooler outside, usually in the evening and at night.
- Fans: can help keep air moving if the temperature is below 35 °C. Don't point one directly at your baby.
- No hats indoors or for sleep.
A baby who's slightly too cool will usually let you know. A baby who's too hot may just become drowsy. When in doubt, fewer layers.
Feeds and fluids
- Under 6 months: breastfed babies don't need water; offer more frequent breastfeeds. Formula-fed babies under six months may need small sips of cooled boiled water in hot weather, as well as their usual feeds.
- From around 6 months: offer sips of water from a cup with meals, alongside breast milk or formula.
- Watch the nappies: fewer wet nappies, or dark pee, can be a sign of dehydration.
Out and about
- Babies under 6 months should be kept out of direct sunlight. Older babies should also stay out of the sun as much as possible, especially between 11am and 3pm.
- Sunscreen: not recommended for babies under 6 months; from 6 months use SPF 30 or higher with UVA and UVB protection.
- Clothing: loose, light clothing and a wide-brimmed sunhat.
- Never cover a pram or pushchair with a blanket or cloth. It can trap heat and cause overheating. Use a parasol or breathable sunshade, and check on your baby regularly.
- Never leave a baby or child alone in a parked car, even briefly.
- Paddling pools can help older babies cool off: keep them in the shade and supervise closely at all times.
Signs of overheating and dehydration
Get medical advice (GP or NHS 111, or your local equivalent) if your baby is hot and sweaty or flushed, unusually drowsy or irritable, feeding less, or has fewer wet nappies or a sunken soft spot on their head. Move them somewhere cool, remove extra layers and offer feeds while you get advice.
Call 999 (UK), 911 (US) or 112 (EU) if your baby is floppy or hard to wake, has a seizure, is breathing fast or with difficulty, or has hot skin and isn't sweating.
Heat rash
Small red or skin-coloured spots on the neck, chest or in skin folds are often heat rash (prickly heat). It usually settles if you keep your baby cool and avoid heavy creams that block sweat. Get advice if your baby seems unwell or the rash doesn't fade when you press it.
Related reading
Sleep, from birth to four: The Big Book of Sleep (PDF, English) is a reference guide to children's sleep, including sleep environment and routines.
Sources
- NHS — Safety in the sun.
- NHS — Heatwave: how to cope in hot weather.
- NHS — Drinks and cups for babies and young children.
- The Lullaby Trust — Room temperature.
Written by the Bloom Guides editorial team. Last updated: 20 October 2026. General information only — not a substitute for advice from your health visitor or doctor.