Why Does Heat Make You Sleepy and Tired?

Who likes being cold? I’d like to think, NO ONE! Being cold makes us snappy, uncomfortable and irritated, but being warm all the time is not something we crave too. If you’ve ever found yourself dozing off in a hot room, or felt sleepy during a long, warm car-ride then you can understand that constant exposure to heat is also not the most desirable thing.

Where heat and warmth are our lifelines, their excess can disrupt certain mechanisms, especially the energy producing centers, in our body leading to fatigue, exhaustion and apparently, a very moody behavior. Well, at least sometimes!

So even though being warm makes us comfortable and relaxed, extended periods of exposure to heat also make us feel tired and sleepy. Here’s why.

Body Temperature Regulation

Heat is an inherent need of our bodies, whether we get it from natural sources like the sun or artificial sources like heaters, air conditioners etc. The reason being a human body and blood have a specified temperature limit and fluctuations in this range can lead to illness. So we may not realize it but our body’s internal energy systems are constantly working to keep our body temperature balanced – not too high, not too low.

This actually means that whenever we are cold and our body temperature drops, our body’s internal energy reserves are used up to warm the temperature back to the specified normal and a significant amount of energy is expanded for this purpose. Conversely, when our body becomes hot, then our internal systems need to cool it down back to normal through sweating.

Many external and internal factors regulate our body temperature including external weather & temperature, your metabolic & heart rate, your food intake etc. All such factors make your body temperature rise or fall and hence, trigger the temperature regulation centers in our body accordingly.

Temperature is actually regulated by breaking down the energy reserves in our body which in turn, are acquired through food and nutrition. So as a result of breaking down that nutrition store and consuming your body energy, you experience fatigue or exhaustion in the aftermath. So whether you are in extremely cold temperatures and your body needs heat or you’re in a hot climate and your body needs to cool down, energy is expanded and consequently, you feel tired.

But warming up your body takes up much more energy than cooling it down. It doesn’t take much energy for your body to pump out sweat onto your skin which is then taken up by the air itself so, not a lot of energy is spent in bringing down your body temperature. But even in such conditions, we start feeling tired and sleepy which brings us to the second reason – Dehydration.



Now another reason for feeling tired and sleepy in the excess of heat is the dehydration factor. In order to cool down the body temperature in a hot environment, our body starts sweating. Sweat consists of water and salts present inside our body and when extra water is lost from the body, our blood starts to lose volume and thicken. This causes the heart to pump blood even harder and expend more energy in the process.

So it’s not the heat itself making you feel sleepy and tired, rather losing water and vital electrolytes from the body along with a considerable amount of energy through exaggerated blood pumping leading to tiredness.

Hot-Cold Cycle

Another very important but not commonly known reason for feeling sleepy because of heat is the following cooling down of the body when removed from the heated environment. For example, when you take a hot bath or drink a hot beverage, your body temperature rises but when that temperature goes down later on, you feel more relaxed and thus, more sleepy.

That is why we sleep better after hot showers. We sleep much more peacefully at cooler temperatures, not in stuffy warmth. So while a hot bath may make you tired, the following cooling down of the body to a more suitable temperature makes your muscles more relaxed and you feel more sleepy.

Psychological Triggers

Psychological Triggers

When around heat, it is not just our physical bodies that react but our brains too. Our brains are programmed to detect patterns in our daily lives. By sensing and cataloging our bodily reactions and feelings to different physical and abstract objects, our brain kind of hard-wires those connections and makes our body react in a similar way in any such situation.

Like being transported to a certain memory or setting when you see or hear a particular image or song. These kind of psychological links are very important in determining our body’s reactions.

So usually when we associate being warm to being cozy and all snuggled up, our brains interpret it as the signal for bedtime because of our usual sleep pattern/routine. When we warm ourselves up, it tricks the brain into assuming that we want to sleep and thus subconsciously, we train our bodies to go into a relaxed mode when warmed enough.

You might think that this fact contradicts the above one about feeling drowsy because of the cooling down of your body but having a cool enough body temperature doesn’t mean you are not still warm. It might be confusing but stay with me.

When the environment is warm to the point of stuffiness or sweating, you can’t sleep soundly so you need to lower the temperature somewhat. Now this temperature drop doesn’t necessarily means going cold, rather just low enough to be comfortably warm.

heat makes me sleepy

How to Tackle Heat Tiredness and Sleepiness?

We all love being cozy and warm but not at the cost of being lazy or drowsy. If you’ve been experiencing hot weather fatigue, here are some tips to counter the tiring effects of heat and warmth:

  1. Stay hydrated, especially in winters when you are employing artificial heating sources everywhere. But avoid diuretics, like alcohol, because they not only make your body lose extra fluids but also damage your kidneys and stomach.
  2. Don’t keep sitting in front of heaters for long periods of time, especially during the day.
  3. Never sleep with the heater on in your room. It is not only a health hazard but also dangerous for your surroundings materials which run the risk of catching fire. You will also become dehydrated like a dried fruit.
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