How hot weather hurts our hearts

by Carolyn Thomas  @HeartSisters

Welcome to Lotus Land, where, alas, it’s been stinkin’ hot lately. This is tragically unfair, I think. I moved here to Canada’s beautiful West Coast decades ago in order to escape the kind of soul-sucking sauna that passes for summer back east.

And because uncomfortably hot weather is so deliciously rare here, few of us even have air conditioning, although I do have a little electric fan that I’ve started carrying around the apartment with me from room to room this past week.

Since surviving a heart attack, I’ve learned a whole new reason to hate the heat.  I walk around feeling sick, clutching my little fan, a damp cloth pressed to the back of my neck, hot and cranky and looking like I’ve been hit by a very large bus. Here’s why heart patients can feel so much worse when those temperatures soar:  

Your Heart in the Heat

The heart is a fist-sized muscle that pumps blood through your arteries to all organs and tissues throughout your body. When ambient temperatures rise, the heart has to beat faster and work harder to pump blood to the surface of your skin to assist with sweating to cool your body.

If your body cannot cool itself enough, strain is put on the heart, and organs can begin to suffer damage – a potentially fatal condition known as heat stroke.

If You Have Heart Disease

Anyone can get heat stroke, but people with heart disease and other cardiovascular diseases are at greater risk.

If you have heart disease, your heart may not be able to work harder in the heat to maintain cooler body temperatures. Additionally, diuretics to reduce water in the bloodstream are prescribed for many heart conditions, as are beta blockers. Each of these medications can reduce a person’s ability to cool off in the heat.

Help Prevent Heat Stroke

  1. Wear loose-fitting, lightweight clothing.
  2. Protect against sunburn.
  3. Drink plenty of fluids (if you’ve been diagnosed with heart failure, talk to your doctor about fluid intake).
  4. Take extra precautions with certain medications (e.g. diuretics or beta blockers as listed above). Ask your doctor or pharmacist if any of your meds affect your body’s ability to stay hydrated or dissipate heat).
  5. NEVER leave anyone in a parked car, even for a very short time.
  6. Take it easy during the hottest parts of the day by finding a cool place.
  7. Take the time to get used to extreme heat (it can take a week or two to get your body used to it).

Exercising in the Heat

Simple rule: when it’s dangerously hot outside, don’t do it, unless you’re exercising inside a comfortably air-conditioned building. If you’re used to exercising indoors or in cooler weather, take it easy at first when temperatures begin to climb. Don’t increase the length or intensity of your workouts if you experience any heat-related symptoms.

Drink plenty of fluids. Dehydration is a key factor in heat illness.

If you’re unfit or new to exercise, be extra cautious when working out in the heat at all, especially if you have a heart condition in which your body may already  have a lower tolerance to the heat. Reduce your exercise intensity and take frequent breaks in the shade to rest and drink water.

Both the exercise itself and the air temperature can increase your core body temperature. To help cool itself, your body sends more blood to circulate through your skin. This leaves less blood for your muscles, which in turn increases your heart rate. If the humidity is also high, your body faces added stress because sweat doesn’t readily evaporate from your skin. That pushes your body temperature even higher.

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

Know the symptoms of heat exhaustion and heat stroke (below). If any of these symptoms appear, stop exercising and cool down immediately by dousing yourself with cold water. You may need to get medical attention. Heat exhaustion can progress quickly to heat stroke, which can kill you.

Symptoms of Heat Stroke

Heat stroke is a medical emergency. If you experience the following symptoms, apply cool water to your skin immediately and seek medical help.

  • High fever
  • Hot, dry skin without sweating
  • Pounding pulse
  • Dizziness
  • Nausea and/or vomiting
  • Confusion
  • Unconsciousness

If you experience heavy sweating with cool, clammy skin, along with symptoms such as fatigue, muscle cramps, headache, nausea, or fainting, you may have heat exhaustion – a form of heat sickness that can lead to heat stroke.

Get out of the heat immediately. Fan your body and apply cool water to your skin, remove extra clothing or any sports equipment, and drink cool (not cold) water or a sports drink; these steps can help you stop heat exhaustion before it worsens.

If these symptoms strike, have someone stay with you if possible who can help monitor your condition.   If you don’t feel better within 30 minutes, contact your doctor.

Remember: if you have signs of heat stroke, seek immediate medical help.

Source: Mayo Clinic, The Heart and Stroke Foundtion, and The Society for Cardiovascular Angiography and Interventions

NOTE FROM CAROLYN: I wrote much more about external factors that can affect women heart patients’ day-to-day life in my book, A Woman’s Guide to Living with Heart Disease (Johns Hopkins University Press, 2017).

UPDATE:  Thanks to Texas cardiologist Dr. John P. Erwin III for sharing with us this study on the effect of hot weather on the heart:

  •  “Relation of Atmospheric Pressure Changes and the Occurrences of Acute Myocardial Infarction and Stroke”, Houck, Philip D. et al. American Journal of Cardiology , Volume 96 , Issue 1 , 45 – 51

Q: What’s your best tip to beat the heat?

28 thoughts on “How hot weather hurts our hearts

  1. Thank you so much for this site!! Just diagnosed with microvascular heart disease, love your book – so much wonderful information.

    Now I don’t feel so alone – THANK YOU! Dr. Sedlak in Vancouver is doing a study on women’s heart disease and microvascular heart disease.

    Liked by 1 person

  2. Pingback: NAME REMOVED: This comment has been removed because the sender was attempting to sell you air conditioning equipment…
  3. This site is so informative and it’s wonderful to know other ladies are experiencing similar symptoms 🤗🤗.

    It’s 2 years since my minor heart attack, I need a small stent which the cardiologist can’t do as where it is will end up blocking again. Also I am severely asthmatic so breathing always a problem. Very fortunately, have relocated to Spain, (cold weather in UK was unbearable). I’ve managed to get fit enough to walk a dog for 30/40 mins a day, but STILL get this fatigue every day after around 4 hours of being up. I’m 64, and until this was always fit having horses + 8 other pets and 2 kids!!! It’s so frustrating.

    Many thanks for this excellent website.

    Liked by 1 person

    1. Lucky you to live in Spain, Shelley! I hope that, when you feel fatigued after being up for 4 hours, you take a nice nap! Plan it right into your daytimer.

      Naps are wonderful – I had to wait until having a heart attack to learn that…


  4. Hi i’m a 21 year old healthy female and I am very concerned about the hot weather right now where I live. It’s 26-28 degrees Celsius outside in the day and it can be as hot as 17 degrees by midnight. My apartment is located to the sun and the air conditioning is very poor, the air is standing still all the time and i’m starting to feel a pressure over my chest and some pain and I have very low energy, my head hurts too. I do struggle with drinking enough water but today i’ve had almost 3 liters which is a lot for me but still the pressure and slight pain in my chest. Should I be concerned?? I sit outside in the evening as there is a very light breeze and the sun is not strong whereas indoors it feels like there’s no air but I have to sleep inside and I don’t have a fan or the energy to go to some store and buy one.
    I have no previous heart problems…


    1. Hi Julia – I’m not a physician so cannot of course comment on your specific situation, but I can tell you generally that the heat that heart patients need to be concerned about is typically far hotter that the temperatures you quote (26-28 Celsius. = 78-82Fahrenheit). That midnight temperature of 17C. is actually cooler than what’s considered to be normal room temperature all year round (20C, or 68F). You may be feeling that it’s hotter than that because of humidity, lack of wind, etc. It’s absolutely not uncommon to feel low-energy during hot weather when we are not yet acclimatized to the heat.

      In fact, it apparently takes a few weeks just for our bodies to adjust to hotter temperatures than we’re used to. Try spending a few hours every day in an air-conditioned environment (movie theatre, community centre, shopping mall, etc) to see if that makes a difference in how you feel. While you’re at the mall, you can go shopping for a fan. If it doesn’t make a difference, you could see your doctor, but it’s likely safe to say that it would be unusual for a healthy 21-year old female to suspect heart disease because of hot weather-related symptoms.


  5. Absolutely, I went into a cool store today for creamers, a blood pressure machine was there. My BP was 96/72, pulse was 121. I was able to get it down but it sure shocked me. Luckily no Angina issues manifested.

    Just have to be more more careful! Thanks for the info! Everyone with cardio issues, stay hydrated and slow down when it is hot!

    Liked by 1 person

    1. Ernie, call your doctor right away to discuss this trouble breathing you’re having. Shortness of breath can be common at first after open heart surgery, especially for smokers or those who already had lung problems (sometimes relieved by deep breathing, walking or coughing) but just check with your doctor first to be on the safe side. Many of my readers tell me they have found relief with a steam vaporizer type of humidifier during the winter months when air is particularly dry.


  6. We have DRY heat here in Colorado. Not to mention high elevation makes us closer to the sun. It helps me to run my humidifier at night in the bedroom. Also, with Congestive Heart Failure, I cannot drink water all at once. So I keep a water bottle in every room & in the car.

    Liked by 1 person

  7. Excellent site, informative, open minded, professional and people friendly. I have learned more from it about my condition, microvascular disease, than from any doctor.

    I want to know whether I am at similar risk of heart attack as people with diagnosable heart disease? Should I have regular check ups and which ones? Can the worsening of the risk factor be diagnosed? When I have symptoms of angina or heart attack when and how do I decide whether to go to see a doctor or go to A@E? Did anyone investigate the link with brain supply of oxygen, in relation to stroke or even alzheimers?

    Liked by 1 person

    1. Thanks for your kind words about my site. I’m not a physician so cannot comment specifically on your case, but I can say that in general you should have regular visits with your cardiologist if you have been already diagnosed with MVD. I can also tell you that I too live with MVD and have chest pain almost every day, sometimes several episodes per day. It takes some day-to-day experience to gauge which symptom is just “normal” refractory angina, and which symptom means you should seek immediate help. Otherwise, I’d be running to the Emergency Department every other day! I’m assuming you have a prescription for nitro for angina; you can learn more about this “wonder drug” here. And if you do a search on this site (upper right corner search box on the black background) for microvascular disease, you’ll fine more info on this diagnosis that may answer lots of your questions. Best of luck to you…


  8. I live in Miami and the sweltering heat and humidity have affected me, to a much greater degree, after my cardiac event. Even walking can be difficult for some.


  9. Both of my kids are in soccer and I have to endure a lot of games in 90+ degrees here in Georgia. It is hard on all of us, but add health conditions and menopause hot flashes to the mix, it is almost unbearable.

    I found a product at my kids soccer equipment supply store. It is called Frogg Toggs(TM) Cooling Chilly Pad Towels. Just dip it in cold water and it stays freezing cold for hours, if the cooling effect wears off, just dip it again, wring it out and off you go. I have seen them on line and at Dicks Sporting goods, they run about $13 and come in all colors. I was told to run cold water over your wrist in a heat emergency, it instantly cools the entire body. Stay cool out there!


  10. What a timely topic – I have been feeling like the same bus has hit me lately.

    I was in Baja MX temps in the 100-110 range and drove to Tucson AZ temps 100-107 range and the same bus has hit me.

    I have an appointment with my Cardiologist this week and we are going to talk about my symptoms, maybe if I hadn’t been in the heat I wouldn’t feel so bad? I seem to have more questions than the doctors have answers for, at least the ones I see.

    Liked by 1 person

    1. Oh my goodness – Mexico! Arizona! I feel way too hot just thinking about those kinds of temperatures. Hope you feel better soon.


  11. As a Microvascular Disease person, I can attest that the heat can immediately “zap” me ~ whether that is a hot day, or a hot car; my body cannot rapidly adjust. My vascular system just can’t compensate. Just as it can’t compensate for exertion or emotion, temperature will do the same thing for me. Ditto for cold.

    I have a medical tip for people, but you will have to communicate to your doctor. PG&E has a rate adjustment allowance for medical equipment and medical necessity. For example, a CPAP is a medically required device, therefore, you would have a credit for EACH CPAP you might have in your home, one allowance per person.

    We recently had to add A/C to our home, because after 5 years of trying to do without it after ridding ourselves of the old one (to be green), I realize that I just function better and need less meds if I can stay cool.

    This summer, a heat wave confirmed this for me. I had more energy and was able to do housework instead of lying in a heap on the sofa all day. Again, the utility company will give you a baseline credit if your doctor signs off on it as “medically necessary”, as they would for asthma, for example.

    Ditto for the IRS. It is a tax deduction of a medically necessary piece of equipment, if your doctor will state that it is.

    Luckily, my cardiologist saw my point, though she had never encountered this request before.

    I suggest that any cardiac or CPAP patient consider employing these financial adjustments ~ because they help!

    Liked by 1 person

    1. Interesting – your cardiologist is basically writing you a prescription for your A/C.

      Like you describe, the heat zaps me relentlessly in a way that’s hard to describe to those who have never felt this. But overnight, the weather broke, we had a bit of a cooling rain shower (while outdoors watching fireworks at Butchart Gardens!) and this morning I feel like a new person. Yay!


    1. Hi Dr. S – I think this is especially true during an unexpected heat wave when we think we can just carry on as usual!


  12. Interesting post. I live in Miami and the sweltering heat and humidity have affected me, to a much greater degree, after my cardiac event.

    If I stand outside, even for a short while, my heart starts to race and I have difficulty breathing. My solution is to get indoors and into the air-conditioning quickly. Needless to say, I spend much of my time indoors. I have thought of moving to a colder and drier climate, but I have heard that the cold is bad as well. I have not lived in the cold for many years so I am unaware of its effects. Maybe your next post will discuss the cold weather? Thanks

    Liked by 1 person

    1. You’re right, Magda – I frequently hear from heart patients who suffer terribly in cold winters. I did briefly cover cold weather here (exercising in the cold) and here (mall walking) but maybe I’ll take your advice and discuss the topic in more detail when winter starts!


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