Does Weather Affect Your Heart?

The relationship between temperature and your heart

Understanding how tomorrow's weather forecast could relate to your heart health may seem unnecessary. But external factors such as heavy rain or a three-day heatwave affect your heart and body more than you realize.

According to Robert H. Shmerling, MD, a senior faculty editor at Harvard Health Publishing, the average temperature of the human body should be around 97.5 degrees (36.4°C)7 with an average heart pulse between 60 to 100 beats per minute. It's thanks to your heartbeats and your cardiovascular system that your body receives the proper oxygen and nutrients. Your cardiovascular system (also called the circulatory system) is responsible for your body's temperature control as well.

Depending on what the body needs at the time, the heart will receive messages letting it know if it needs to pump more or less blood. For example, when sleeping, the heart only needs to circulate enough blood to provide the smaller amounts of oxygen required when the body is at rest. But when exercising, the body sends messages that it needs much more oxygen than usual, making the heart pump faster, increasing your heart rate8.

TIP: If you own a fitness watch, your resting heart rate (RHR) will always be available to you when you need it. If you haven't invested in a fitness wearable yet, no worries! To find out what your RHR is, hold two fingers on the inside of your wrist below your thumb until you feel a pulse, then count each beat for one full minute. Do so as many times a day as needed.

So how does HOT weather affect the heart?

In hot weather, your cardiovascular system starts working overtime to try to keep your body temperature at normal levels. It will do two things as a result: radiate heat and make you sweat. Though this extra effort is typical, it may signify that your health is in jeopardy in some circumstances. Especially if you are already at high risk for heart disease.

Question: Do heat and hot weather increase my resting heart rate? Answer: Yes.

If the air temperature is the same or hotter than your body temperature, the heart starts pumping faster and reroutes some of the blood to the skin to help radiate that extra heat3. That means that in hotter weather, the body's temperature is going to climb as well. This is because the body's goal is to make sure that its temperature is warmer than the air around it.

Did you know? Your heart circulates two to four times more blood per minute on a particularly hot day than on a cool day.

This radiating of heat and rerouting blood to the skin also creates sweat. Every bead of sweat that evaporates from your skin helps cool your body as it takes away some of the heat. However, evaporation demands more of the cardiovascular system as well. The more you sweat, the more water and minerals you lose (minerals such as chloride, sodium, and potassium). This could lead to dehydration and a higher risk of heat stroke, a condition caused by overheating.

Just for safety reasons, here are the symptoms of a heat stroke:

  • Sweating
  • Cold clammy skin
  • Dizziness
  • Fainting, nausea, vomiting
  • Muscle cramps
  • Swollen ankles
  • Shallow or fast breathing

If you recognize the symptoms of a heat stress, you should drink plenty of water and fluids, move to a cooler area (even better if air-conditioned), lie down, and if available, shower in cool water. When in doubt, always contact your doctor or local hospital for more information.

What can you do to keep cool? Here are some simple tips and tricks that you can do to help regulate your body temperature and save your heart while in hot weather2:

  • Stay hydrated - drink plenty of water
  • Avoid drinking alcoholic drinks
  • Wear light, loose-fitting clothing
  • Eat cold foods with high water content such as vegetables and fruits (also a good source of vitamins and minerals)
  • Stay out of the sun during the hottest part of the day (from 11am to 3pm)
  • If you go out, apply sunscreen, wear a hat and bring water
  • Avoid high-intensity physical exercise

How does HUMIDITY affect the heart?

Humidity in hot weather affects the cardiovascular system, making it harder for your body to cool down.

As mentioned in the 'How does HOT weather affect the heart?' section, your body cools itself down by radiating and sweating. However, your body will only cool down if your sweat can actually evaporate. As there are many water particles in the air in humid weather, your sweat starts to evaporate more slowly. Your body temperature then has a more challenging time cooling down, and its temperature may continue to rise.

This is especially noticeable when exercising, as you create more heat and produce more sweat during physical exertion.

How does COLD weather affect the heart?

Have you heard that more heart attacks happen in cold water than in warm water? It's not a myth!

As the temperatures drop around you (whether the air or the water), your blood vessels start to tighten and constrict in response. At the same time, as your blood vessels constrict, your heart starts beating faster to speed up your blood flow in trying to help keep your body warm1. This is where problems usually happen.

Since the cold makes the blood vessels more narrow, the amount of blood flowing decreases, meaning less oxygen and nutrients can reach different parts of your body. Your heart will have to increase the number of beats, increasing your heart rate to provide the necessary oxygenated blood and nutrients to your body. This is why, on average, your blood pressure and cholesterol rise in colder weather1.

In colder weather, a quick spike in your blood pressure, especially while doing physical activity (like shoveling snow), can cause severe health and heart issues such as4:

  • Unstable chest pain
  • Heart attack
  • Stroke

Some of the best ways to prevent heart-related problems from arising in the colder months of the year are to be aware of the complications, know the risk, and stay warm. Especially if you go outside and are planning to be physically active. Make sure to wear the appropriate clothing to help stay warm and comfortable- dress in layers!

Most importantly, maintaining a heart-centered lifestyle throughout the year and managing your blood pressure is key to preventing heart diseases such as heart attacks and strokes.

Don't wait until it's too late. By tracking your heart metrics, you'll be able to notice any changes or abnormalities firsthand, and with your doctor, have the knowledge to help prevent heart disease.


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