Why do I feel sleepy when I get warm? Another frequently asked question - I feel tired when i'm warm...but cold is the secret to sleeping better.

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It’s a drop in temperature that actually triggers sleep.  Warmth does not trigger sleep per se. So why do so many people report feeling sleepy when they get warm? 

This is likely due to the combination of a couple of things.  Firstly, it’s hard work. When you get warm your blood pressure drops.  Less oxygen gets to your brain and your body has to work a little bit harder.  This can make you feel tired. Secondly, your body and brain associate warmth with safety and comfort.  Since birth you’ve been associating this with sleep. As such, you’ll feel tired and safe when warm and comfortable.

It’s also very likely that people notice feeling tired in the evening, after eating dinner or in the lounge watching a bit of T.V.  This happens to be a time when we keep our house nice and warm. As such people associate feeling tired when warm.

Heat, rather than warmth, can lead to you feeling sleepy.  This is usually due to dehydration, changes in blood pressure, your body working hard to keep you at a constant temperature and sudden drops in temperature often due to moving from heat to air-conditioned rooms.

Written by
Sam Billington

Sam is our sleep guru. I am fascinated by sleep and I've used my science training to research and learn about sleep. I have been providing sleep advice and personal sleep plans for years. My day job is Head of Workplace Culture in Defra, I live in London with my wife and have a PhD in Ecology and Biology.