Bedroom temperature: how heat and cold affect sleep

• Heat and humidity mean more awakenings and less deep sleep.
• A cool room with warm bedding is best for most people.
• A warm shower 1 to 2 hours before bed may help you fall asleep.
• During winter outages, insulate the bed, not just the room.

What the research shows

A review of studies on the thermal environment and sleep found that heat exposure increases wakefulness and reduces slow-wave and REM sleep, and that high humidity makes these effects worse. Cold exposure had less effect on sleep stages when people were adequately covered, although it can affect heart function (Okamoto-Mizuno & Mizuno, 2012).

A comfortable bedroom is a standard part of sleep hygiene (Irish et al., 2015; Altena et al., 2020).

In practice

• Keep the bedroom cool and ventilated, with a warm blanket you can adjust.
• Use breathable cotton or linen bedding.
• Take a warm shower or bath 1 to 2 hours before bed.
• In hot weather, use fans, close blinds during the day and ventilate at night.
• In cold weather or power outages, add layers to the bed: a sleeping bag, extra blankets and a pad underneath.