Summer in Oklahoma often brings prolonged periods of extreme heat, with temperatures frequently reaching the upper 90s and triple digits. Combined with high humidity, these conditions place additional demands on the cardiovascular system. While anyone can be affected by extreme heat, people living with heart or vascular disease are more likely to experience symptoms or complications because their cardiovascular system is already working harder to compensate for an underlying condition.
At CardioVascular Health Clinic, our physicians diagnose and treat the full spectrum of heart and vascular conditions, including coronary artery disease, peripheral artery disease, heart rhythm disorders, heart failure, venous disease, and carotid artery disease. Cardiovascular disease affects every patient differently, so understanding how seasonal changes–including heat–influence the heart and circulatory system is an important part of helping patients manage their health year-round. Since many cardiovascular conditions can become more symptomatic during periods of extreme heat, our team encourages patients to recognize changes in their activity tolerance and seek evaluation when symptoms become persistent or progressively worse.
Your cardiovascular system does much more than circulate blood. It also plays an essential role in regulating body temperature. According to Dr. Sherisa Warren, an interventional cardiologist at CardioVascular Health Clinic, one of the biggest misconceptions about extreme heat is that people often underestimate how much additional work it creates for the heart, particularly in patients who already have underlying cardiovascular disease.
Whenever your body begins to warm, the heart and blood vessels work together to help release excess heat. Blood vessels near the surface of the skin widen and relax (dilate), allowing more warm blood to circulate closer to the skin where heat can dissipate into the surrounding air. At the same time, the heart pumps more blood throughout the body while continuing to supply oxygen and nutrients to the brain, muscles, kidneys, and other vital organs.
However, while blood vessel dilation and increased cardiac workload help the body to cool itself, they can also affect blood pressure and circulation, making it more difficult for the cardiovascular system to maintain its normal balance. The longer someone remains in extreme heat—or the more physically active they are while outdoors—the greater those demands become. Healthy hearts generally have enough reserve, or extra capacity, to meet those increased demands. When heart or vascular disease is present, however, much of that reserve may already be in use, leaving less ability to adapt to additional stress.
"Most healthy hearts can adapt to these changes," says Dr. Warren. "The concern is when the heart is already working harder because of an underlying condition. Extreme heat can reduce the amount of reserve the cardiovascular system has to respond to additional stress, so the question isn’t whether your heart is working harder but whether it has enough reserve to handle that additional workload.”
Extreme heat does not cause cardiovascular disease, but it can make existing conditions more symptomatic. As the heart and blood vessels work harder to regulate body temperature, underlying heart or vascular disease may become more apparent, even if it previously caused few or no noticeable symptoms.
"One of the things we hear from patients is that activities they've done comfortably for years like mowing the lawn or going for a daily walk suddenly become much more difficult and tiring in the heat," Dr. Warren says. "Those changes shouldn't automatically be dismissed as simply getting older or not tolerating the heat. They may be an early sign that an underlying cardiovascular condition deserves evaluation."
Heat places additional stress on the cardiovascular system, but the way that stress affects patients varies depending on the underlying condition. Some cardiovascular diseases become more symptomatic during periods of extreme heat, while others primarily affect a person's ability to tolerate physical activity or regulate body temperature.
Symptoms that occur repeatedly or worsen during periods of extreme heat—or activities that suddenly become much harder than they were in previous years—deserve medical attention. Rather than assuming "it's just the heat," these symptoms should be discussed with your cardiovascular specialist and evaluated as signs of possible cardiovascular conditions.
"Patients know their bodies better than anyone," Dr. Warren says. "If something that used to feel easy suddenly becomes difficult, especially during periods of extreme heat, it's worth talking to your physician. We'd much rather evaluate symptoms early than after they become an emergency."
Extreme heat increases the heart's workload and oxygen demand. For patients with coronary artery disease, narrowed coronary arteries may not be able to supply enough blood to meet those increased demands, making symptoms such as chest discomfort, unusual fatigue, or shortness of breath more noticeable during physical activity.
"Heat doesn't create coronary artery disease," Dr. Warren explains. "What it often does is increase the heart's workload enough that symptoms become noticeable sooner than they otherwise would."
Peripheral artery disease affects blood flow to the legs and feet, often causing pain, cramping, or fatigue while walking, and patients with PAD may find that walking becomes more difficult during periods of extreme heat. Because the cardiovascular system is already working harder, leg pain, cramping, or heaviness may develop sooner than usual, reducing walking distance or limiting outdoor activities. Talk to your doctor if you experience a noticeable decline in walking tolerance because, while weather can influence symptoms, worsening claudication may also indicate progression of peripheral artery disease.
For patients with heart failure, extreme heat places additional demands on a heart that may already have reduced pumping ability. Routine activities can become more tiring, and symptoms such as fatigue, shortness of breath, or decreased exercise tolerance may become more pronounced during hot weather. Persistent or worsening symptoms should be discussed with your physician.
The additional cardiovascular stress created by extreme heat may make heart rhythm disorders more noticeable in some patients. Episodes of palpitations, irregular heartbeat, or exercise intolerance may occur more frequently or become more symptomatic, particularly during prolonged outdoor activity. New or worsening rhythm-related symptoms should be evaluated by your doctor.
Carotid artery disease affects blood flow to the brain, making any new neurological symptoms especially important. Dizziness, sudden weakness, vision changes, difficulty speaking, or loss of coordination should never be attributed solely to the heat, as they may indicate a medical emergency requiring immediate attention.
Heat naturally causes veins to widen, which can worsen symptoms of chronic venous insufficiency. Patients may notice increased swelling, heaviness, aching, or fatigue in the legs after prolonged standing or spending time outdoors. Compression therapy, regular movement, and limiting prolonged heat exposure may help reduce symptoms.
Some medications commonly prescribed to treat heart and vascular disease may also influence how the body responds to extreme heat. Medications that lower blood pressure, slow the heart rate, reduce fluid retention, or relax blood vessels are essential for managing many cardiovascular conditions, but they may also affect how your body adapts during periods of prolonged heat.
That doesn't mean these medications should be stopped or adjusted during the summer.
"Patients should never stop taking prescribed heart medications because of hot weather," says Dr. Warren. "If you're having difficulty tolerating the heat or notice new symptoms, that's a conversation to have with your physician and not a reason to stop treatment."
Summer in Oklahoma is about more than high temperatures. Across much of the state, prolonged periods of extreme heat are frequently accompanied by elevated humidity, causing the heat index—or "feels like" temperature—to climb well above the actual air temperature.
Humidity makes it more difficult for sweat to evaporate, reducing one of the body's primary methods of releasing excess heat. As a result, the heart and blood vessels must continue working harder—and often for a longer period of time—to regulate body temperature. That's why a humid 94-degree afternoon may feel considerably more taxing than a hotter but drier day.
According to the Oklahoma State Department of Health, Oklahoma recorded more than 140 heat-related deaths between 2013 and 2022, with the overwhelming majority occurring during the summer months. While many people associate heat-related illness with heat exhaustion or heat stroke, cardiovascular disease is one of the most significant underlying health conditions that increases the risk of serious complications during periods of extreme heat. In addition, air quality often declines during the hottest days of summer, creating another source of stress for people with cardiovascular disease. Heat, humidity, and poor air quality together can create conditions that are especially challenging for the heart and circulatory system.
For many Oklahomans, staying indoors all summer simply isn't realistic; yard work, gardening, fishing, golf, youth sporting events, ranch work, and other outdoor activities are part of everyday life. Living with cardiovascular disease doesn't mean avoiding summer altogether, but it does mean being mindful of how heat affects your body. By understanding how heat and humidity affect your cardiovascular system—and by planning activities around weather conditions rather than simply the calendar—you can help reduce unnecessary cardiovascular strain. Even small changes in routine can significantly reduce the stress placed on your cardiovascular system during Oklahoma's hottest months.
Not every symptom experienced during hot weather is an emergency, but persistent or recurring cardiovascular symptoms should never be ignored. If you notice that routine activities suddenly become much more difficult than they were in previous summers, or if you consistently experience chest discomfort, unusual shortness of breath, worsening leg pain while walking, increased swelling, or more frequent heart palpitations during hot weather, schedule an appointment with your cardiovascular specialist.
Heat may contribute to these symptoms, but it should never be assumed to be the only cause.
If hot weather is making everyday activities more difficult, don't assume it's simply part of getting older or a normal response to the Oklahoma summer. At CardioVascular Health Clinic, our physicians diagnose and treat the full spectrum of heart and vascular conditions using advanced diagnostic technology and comprehensive cardiovascular expertise. If you've noticed changes in your exercise tolerance, circulation, or heart-related symptoms, schedule an evaluation today so you can better understand what's causing them and receive the care you need.
