If you’ve ever nodded off in a hot meeting room or found yourself quickly falling asleep on a long, warm car journey, you know that heat can make you tired.
But why is this?
Here are five main reasons why heat can make you feel sleepy.
Often, it’s not the heat itself making you tired, but the dehydration that comes with it. Losing fluid and salt through sweating can quickly lead to dehydration, which usually leads to tiredness. If you find yourself getting sleepy because you’re hot—and you were previously feeling wide awake—then you should probably have a decent drink of water to stave off further effects. Of course, there’s no guarantee it’s this, but it’s always worth being cautious.
Trying to keep cool
Similar to the above reason, your body will expend energy in an attempt to keep cool—sweating is just one of these ways.
Expanding energy is what makes us tired, and though we usually think of that in terms of energetic activity (like running), keeping your body at a consistent temperature does just the same. It’s not surprising then that on hot days you’ll start to feel tired.
We often think of being warm as being cozy and being cozy as being all snuggled up and ready to sleep. This psychological link can be stronger than you might think! You know how sometimes you’ll hear a certain song, or smell something particular, and you’re whisked straight back at a specific time or place in your past? It’s the same with this—when you associate something so strongly with a feeling, it often becomes linked.
So when you’re warm, it’s easy for your mind to think of this as sleepy time and for you to react accordingly. Interestingly, you can use this trick to design the perfect place for sleep if you’re having sleeping troubles.
Low blood pressure
When it gets warm, your blood pressure will drop. For most people this is fine, but if you get headaches and nausea, it’s worth going to a doctor.
Generally, a slight drop in blood pressure only means that there is less amount of blood reaching your brain, so there is less oxygen going there, and your body will, therefore, get tired as it struggles to do the same amount of stuff as usual.
It might seem strange to list ‘cooling down’ in an article about heat, but it’s actually one of the key reasons! When you start to fall asleep, your body temperature drops. Therefore, attempting to emulate this can make you sleepy—for instance, having a warm bath or a hot drink will make your temperature rise, and then the following drop can make you sleepy.
So remember—even though heat might make you tired, if you really want to sleep, the heat might not be the most important thing! Make sure your mattress (see top picks) and bedding don’t retain heat too well, or you may find you end up having quite a restless night.
While heat is excellent at making you feel sleepy, it’s not necessarily the best for keeping you asleep. We sleep better at cooler temperatures. Plus, being asleep in a hot room makes it easier to fall pretty to dehydration as mentioned earlier. We recommend keeping your room at a reasonable temperature and using methods like hot drinks, baths, and piles of (movable!) blankets to apply heat to your advantage rather than letting it become a hindrance.