Why the Hot Weather Makes You Tired: The Science Behind Heat and Fatigue

Have you ever wondered why you feel more tired and sleepy when the weather is hot? You are not alone. Many people experience a drop in energy and motivation during the summer months, especially when the temperature rises above 90 degrees Fahrenheit. But what causes this phenomenon? How does heat affect your body and brain? And what can you do to prevent or reduce heat-related fatigue? In this article, we will explore the science behind heat and fatigue, and share some tips and tricks to help you stay cool and alert in the hot weather.

How Heat Affects Your Body

When the weather is hot, your body has to work harder to maintain its normal temperature of 98.6 degrees Fahrenheit. To do this, your body uses two main mechanisms: increasing blood flow to the skin and sweating.

Increasing blood flow to the skin helps to dissipate heat from your body to the environment. However, this also means that less blood is available for other organs, such as your brain, heart, and muscles. This can reduce the amount of oxygen and nutrients that reach these organs, and impair their functioning.

Sweating helps to cool your body by evaporating water from your skin. However, this also means that you lose fluids and electrolytes, such as sodium and potassium, that are essential for your body’s balance and performance. If you don’t replenish these losses by drinking enough water and eating salty foods, you can become dehydrated and experience symptoms such as thirst, dry mouth, headache, dizziness, weakness, and confusion.

Both of these mechanisms can lead to fatigue and lethargy, as your body uses more energy and resources to cope with the heat. You may also feel less motivated, alert, and focused, as your brain function is affected by reduced blood flow and dehydration.

How Heat Affects Your Sleep

Another factor that can contribute to heat-related fatigue is the quality and quantity of your sleep. Sleep is vital for your health and well-being, as it helps to restore your body and brain, regulate your hormones, and consolidate your memory and learning. However, when the weather is hot, your sleep can be disrupted and compromised.

One of the reasons is that your body temperature follows a natural cycle that fluctuates throughout the day and night. Typically, your body temperature drops at night, signaling your brain that it is time to sleep. However, when the weather is hot, your body temperature may not drop enough or may rise due to the heat, making it harder for you to fall asleep and stay asleep.

Another reason is that the heat can make you uncomfortable and restless, especially if you are sweating, wearing heavy clothing, or sleeping in a poorly ventilated room. You may also have trouble finding a comfortable position, as your body tries to avoid contact with warm surfaces. These factors can prevent you from entering the deeper stages of sleep, where most of the restorative processes take place.

As a result, you may wake up feeling tired, groggy, and irritable, and have difficulty concentrating and performing during the day. You may also feel more sleepy and drowsy, as your body tries to compensate for the lack of quality sleep.

How to Prevent or Reduce Heat-Related Fatigue

The good news is that there are some simple and effective ways to prevent or reduce heat-related fatigue and enjoy the summer without feeling drained and exhausted. Here are some of the tips and tricks that you can try:

  • Stay hydrated. Drink plenty of water and fluids throughout the day, especially before, during, and after physical activity or exposure to the heat. Avoid alcohol, caffeine, and sugary drinks, as they can dehydrate you and interfere with your sleep. You can also eat foods that have high water content, such as fruits, vegetables, soups, and salads.
  • Stay cool. Avoid direct sunlight and seek shade or air-conditioned places when possible. Wear light, loose, and breathable clothing, and protect yourself from the sun with hats, sunglasses, and sunscreen. You can also use fans, ice packs, wet towels, or cold showers to cool yourself down. Avoid using ovens, stoves, or other heat-generating appliances, and limit your use of electronic devices, as they can emit heat and disrupt your sleep.
  • Stay rested. Try to get enough sleep and follow a regular sleep schedule. Avoid napping during the day, as it can interfere with your night-time sleep. Make your bedroom cool, dark, and quiet, and use curtains, blinds, or shades to block out the light. You can also use fans, air conditioners, or humidifiers to create a comfortable temperature and humidity level. You can also try sleeping on a lower floor, as heat rises, or sleeping alone, as sharing a bed can increase your body heat.
  • Stay active. Exercise regularly, but avoid doing it during the hottest part of the day, usually between 10 a.m. and 4 p.m. Choose cooler times, such as early morning or evening, or indoor locations, such as gyms or pools. You can also opt for low-intensity activities, such as walking, yoga, or swimming, rather than high-intensity ones, such as running, cycling, or lifting weights. Drink water before, during, and after your exercise, and wear appropriate clothing and footwear. Stop and rest if you feel dizzy, nauseous, or faint, and seek medical attention if you experience signs of heat exhaustion or heatstroke.


Heat and fatigue are closely related, as the hot weather can affect your body and brain in various ways. However, by following the tips and tricks mentioned above, you can prevent or reduce heat-related fatigue, and enjoy the summer without feeling tired and sleepy. Remember to stay hydrated, cool, rested, and active, and listen to your body’s signals and needs. Stay safe and have fun in the sun! 😎

Some facts and figures related to hot weather are:

  • According to NOAA, extreme heat is the leading cause of weather-related deaths in the United States, averaging 138 fatalities per year between 1990 and 2019.
  • According to NASA, the year 2020 tied with 2016 as the warmest year on record since 1880, with a global average surface temperature of 1.84 degrees Fahrenheit (1.02 degrees Celsius) above the 1951-1980 mean.
  • According to Earth Networks, the hottest city in the United States is Phoenix, Arizona, with an average of 168 days of 90 degrees Fahrenheit or above per year, followed by San Antonio, Texas, with 113 days, and Orlando, Florida, with 106 days.
  • According to Verywell Mind, some of the signs of heat-related fatigue include racing thoughts, difficulty making decisions, feeling restless, or feeling detached.
  • According to Medical News Today, a recent study suggests that the desire for a mid-afternoon nap could be biologically determined and affected by external temperatures, as scientists discovered a “distinct thermometer circuit” in the fruit fly brain that responds to temperatures above 77 degrees Fahrenheit.