Overheating during sleep is a recognised risk factor for SIDS; official guidance recommends a room temperature of 16–20°C and checking a baby's chest or neck for signs of excess warmth.
Overheating occurs when a baby's body temperature rises beyond safe limits during sleep, typically due to excessive clothing, bedding, or a warm environment. The Lullaby Trust states that "the risk of sudden infant death syndrome (SIDS) is higher in babies who get too hot." Research cited by The Lullaby Trust indicates that "babies are safer being cooler than being too hot."
What room temperature is recommended?
The Lullaby Trust and the NHS both recommend a room temperature of 16–20°C for infant sleep. The Lullaby Trust notes this is intended as a guide: "Every baby is different and our advice on the ideal room temperature for babies is intended as a guide only." A room thermometer is recommended to monitor temperature, and The Lullaby Trust suggests sleeping in the same room as a baby to help observe conditions.
How can carers tell if a baby is too warm?
The Lullaby Trust advises feeling the baby's chest or back of the neck to assess temperature: "If your baby's skin is hot or sweaty, remove one or more layers of bedclothes or bedding." The hands and feet are noted as normally cooler than the core, and are not reliable indicators of overall body temperature. Babies should not wear hats indoors and should not sleep under duvets or quilts, as these increase overheating risk.
What products and situations increase overheating risk?
The Lullaby Trust specifically advises against weighted swaddles, blankets, and sleeping bags for babies under one year due to overheating risk. The NHS cautions that babies must never sleep "with a hot water bottle or electric blanket, next to a radiator, heater or fire, or in direct sunlight." In very hot weather, The Lullaby Trust states it is appropriate for a baby to sleep in a short-sleeved vest or even just a nappy.
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