Assuming you’re not chasing Gisele Bündchen in your dreams, here’s what’s happening: your skin’s nerve endings carry signals to your brain that tell it to keep your body temperature within a certain range.

When you settle down at bedtime, those nerves go from signalling your brain to keep you cool – because you’re up and active – to telling it to keep you warm, since you’re generating less heat, says University of Oklahoma professor Dr Barbara Holtzclaw. “But when your core temperature settles into its natural range, blood that was sent inwards goes back out towards your skin surface, making you feel warmer,” she says.

“Lying under a heavy duvet can cause some people to start sweating.” Consider switching to covers made with fabric designed to help you maintain your temperature.