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Why Does Heat Make You Tired?

Lara Vargas


When your body is subjected to increased temperatures, it has to work extra hard to maintain a consistent internal temperature. The extra labor of maintaining normal temperatures causes the body to become lethargic. In this article, we will discuss the reasons why body temperature spikes, how you can prevent yourself from overheating, and why heat makes you tired.

How the Body Maintains Temperature

High temperatures cause a body response called vasodilation, which is the dilation of blood vessels. Vasodilation increases blood flow near the skin surface to cool the blood—this is why the skin flushes after body temperatures increase.

Vasodilation also causes the skin to sweat, which cools the skin as it evaporates; however, to do this, heart rate increases, which can stress the body and exhaust you.

Reasons Why Heat Makes Your Sleepy

There are several external factors that make your body temperature spike, such as your environment. The degree of humidity of the air and air circulation plays a role in how much your body temperature rises, and internal factors like heart rate and blood pressure can also cause you to run warm and make you feel tired. 


Dehydration is caused by the loss of fluids and salt through sweating—usually leading to tiredness.

Many people spend their lives slightly dehydrated. When the body secretes sweat to decrease internal temperatures, dehydration worsens and may cause fatigue.

In the case of a sunburn, the body diverts fluids to the burn to repair skin damage, causing the body more work. The diversion of fluids from other body parts also prevents sweating and causes overheating.

Low Blood Pressure

Warm temperatures cause your blood pressure (BP) to drop. A slight drop in BP can make you tired because decreased blood flow means less oxygen reaches the brain, causing the body to struggle to perform tasks it normally does easily.

Psychological Links

It’s common for someone to make a connection between a sound, taste, texture, or sight and something else completely unrelated. When you associate a feeling or action with certain conditions—for example, a warm environment with sleeping—you’ll find yourself falling asleep when warm.

Emotions, like anxiety, can make your body temperature rise and the skin to vasodilate. Although this is generally not long-lasting,” says Dr. Renata Riha of Edinburgh University’s Sleep Research Unit. “Hormonal changes, such as loss of estrogen during menopause, can also play a role,” she adds. 

Avoiding Heat Fatigue

There are ways you can help your body maintain a consistent temperature. Follow our tips below to stay comfortable throughout the hot summer months.

Stay in the Shade

While you need vitamin D to stay healthy, it’s best to stick to the shade during hot weather. Too much sun exposure can increase the risk of heat exhaustion, which is a serious condition involving rapid pulse and heavy sweating as your body overheats.

On days you cannot avoid the sun, put sunscreen on to shield your skin from the ultraviolet rays, preventing sunburn. Wear a hat. Increasing air circulation around your body, for example, by using a fan, can also help.

Staying in the shade shouldn’t disrupt your circadian rhythm (the internal clock responsible for keeping a consistent sleep and wake cycle). As long as you go outside several times a day, you shouldn’t feel tired while following a typical day-to-day schedule.

Stay Hydrated

If you find yourself becoming tired, drink plenty of water to restore your fluid levels. We recommend room temperature water instead of cold water as lukewarm water absorbs better into the body, helping you cool down faster.

Eat Salty Snakes

Eating a salty snack, such as pretzels, helps your body regulate internal temperature by restoring salt and electrolytes.

Take Breaks

Taking breaks on hot days or when you’re engaged in strenuous physical activities gives your body time to cool down before taking on more tasks.

Cooling Down for Sleep

When the body prepares for sleep, it naturally drops its temperature. Emulating this natural reaction before bedtime can trick your body into increasing melatonin production and make you feel tired.

You can raise your body’s temperature by taking a warm bath or drinking a warm drink.


There are many ways your temperature can spike: dehydration, low blood pressure, as well as psychological and hormonal links. If you take care of yourself by drinking enough water, eating healthy, staying out of the sun on hot days, and taking breaks during physical labor projects, you shouldn’t have to worry about suffering sleepiness at random times.

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