Hot weather and your heart

A family having a picnic Summer is here, and while many of us have been longing for the hot weather, it's still important to look after yourself in the heat.

How does hot weather affect my heart?

When the weather is hot you sweat to control your body temperature, but this means that you may lose more fluid than usual from your body. This can lead to a drop in your blood pressure. 

This is not a problem for most people as long as they drink plenty of fluids to keep from getting dehydrated.

However, if you have a heart problem, extreme heat may place an extra burden on your heart and circulation, so it’s particularly important to stay cool and look after yourself. 

What can I do to keep cool?

  • Keep hydrated by drinking plenty of water or other drinks, though if you've been told to restrict your fluid intake, because you have heart failure for example, you should speak to your GP
  • Avoid drinking too many alcoholic or caffeinated drinks. They can cause you to lose more fluid from your body and make you more dehydrated
  • Enjoy cold foods, such as salads and fruit which have a high water content and are good sources of vitamins and minerals
  • Make sure your home is cool when you're staying indoors
  • Wear light, loose-fitting cotton clothes
  • Stay out of the sun in the hottest part of the day between 11am and 3pm
  • When you go out, apply sunscreen, wear a hat and carry some water with you
  • Avoid extreme physical exercise.

Hot weather and heart conditions


If you use a GTN spray to control your angina you should take extra care in hot weather. GTN spray can dilate your blood vessels quickly, which causes your blood pressure to suddenly drop and you may feel faint.   

Heart failure

It’s particularly important to stay cool if you have heart failure - where your heart doesn't pump blood around your body as well as it should. If you’ve been told to restrict your fluid intake, speak to your GP about other ways to keep cool during summer. If you take water tablets and are dizzy or light headed let your doctor know. Your medication can then be reviewed or adapted as necessary.

Heat stroke

Losing too much body fluid can increase your internal body temperature, which could be life-threatening if left untreated. 

Symptoms of heat stroke include sweating, cold clammy skin, dizziness, fainting, muscle cramps, heat rash, oedema (swelling) in the ankles, shallow or fast breathing, nausea and vomiting. 

If you suspect that you or someone else has heat stroke, get medical attention immediately.

Who is most at risk?

Elderly people and very young children have more difficulty in regulating their temperature and so can be more at risk from extreme temperatures. In hot weather, check on your friends and relatives regularly to make sure they are cool and comfortable.

More information and support