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Hot Weather and Cardiovascular Disease

How does hot weather affect the heart?

Extremely hot weather may cause dehydration, heat exhaustion and heat stroke. These risks increase when the humidity is above 70% and the temperature is above 70* F . Heat and humidity interfere with the body’s natural cooling process.

Exercising / Working outside in hot and humid conditions can be hard on your heart.

This is true even for athletes who haven’t yet adapted to the heat. The problem is made worse because the heart is trying to deliver blood and oxygen to your working muscles while your body is trying to cool off by sweating. If you sweat too much, you lose fluid. This decreases your total blood volume. That means your heart has to pump even harder to get the smaller volume of blood to your working muscles, skin and the other body parts. When you lose too much fluid, your body temperature rises and your nervous system doesn’t work properly. Extreme fluid loss can lead to brain and heart damage.

A good way to monitor your body fluid level is to weigh yourself every morning after using the bathroom. If you weigh two pounds less than normal in the morning, you’re probably dehydrated and need to drink more water before doing any vigorous physical activity. (You may have lost water weight. Not fat or muscle tissue .) The National Academy of Sports Medicine suggests all people should drink 96 ounces of water every day. More water will be needed while exercising or working in extreme heat and humid conditions.

If you plan to exercise / work outside in hot and humid weather, wear very light, comfortable clothing and exercise / work in the early morning or late evening, if possible.

Know the symptoms of heat exhaustion and heat stroke.

What are the symptoms of heat exhaustion?
  • heavy sweating
  • cold, clammy skin
  • dizziness or fainting (syncope)
  • a weak and rapid pulse
  • muscle cramps
  • fast, shallow breathing
  • nausea, vomiting or both
What are the symptoms of heat stroke?
  • warm, dry skin with no sweating
  • strong and rapid pulse
  • confusion and/or unconsciousness
  • high fever
  • throbbing
  • headaches
  • nausea, vomiting or both

You can learn the symptoms of these and other life threatening illnesses by participating in one of Go Life Savers CPR & First Aid Training courses.

If any symptoms appear, stop exercising / working and cool down immediately by dousing yourself with cool water. You may need to get medical attention. Heat exhaustion can progress quickly to heat stroke, which can kill you.

Safety First!

– Mark L. Hughes, B.A., NASM-CPT, MBA


Go Life Savers, LLC is dedicated to serving your community by teaching CPR AED and First Aid life saving skills.

You can request a Go Life Savers certification class based on your preferences. Just fill out the form and we will contact you regarding your request within 24 hours.