What Happens to Your Blood Pressure When It’s Hot Outside

Temperature and blood pressure have an inverse relationship, meaning that when the temperature increases, your blood pressure decreases.

How Heat and Humidity Lower Blood Pressure

The human body maintains an average internal temperature of 98.6 degrees Fahrenheit. When exposed to hot environments, the body works hard to avoid overheating, which can impact blood pressure.

Here’s what happens in your body as it works to cool off:

• Blood vessels close to the skin’s surface widen (a process known as vasodilation).
• As blood vessels widen, the heart beats faster and harder to maintain blood pressure.
• Sweating increases and cools your skin off as it evaporates.
• The body’s fluid balance has changed due to sweat loss, so you may experience symptoms of dehydration and thirst for more water to restore balance.

Humidity can further impact blood pressure. Humidity makes it harder for your body to cool off because sweat doesn’t evaporate as efficiently. Your body may work harder to cool off, lowering blood pressure and putting more strain on your heart.

Warning Signs to Watch For

As temperatures heat up, it’s important to monitor your heart health, especially if you have a pre-existing condition that affects thermoregulation, your body’s ability to adjust to changing temperatures.

One way to monitor your health is to watch for heat exhaustion symptoms, including:

• Dizziness and passing out
• Headaches
• Muscle cramps
• Nausea
• Skin that’s pale, cold, and wet
• Vomiting
• Weak and fast pulse
• Weakness

Left unaddressed, heat exhaustion can progress to a medical emergency known as heat stroke. Warning signs include:

• Confusion
• Dizziness
• Feeling hot, including a body temperature of 103 degrees Fahrenheit or higher
• Headache
• Passing out
• Skin that’s flushed, hot, and dry or damp
• Strong and fast pulse

Who Is At Risk?

Groups at a particularly high risk of dropping blood pressure or experiencing heat stroke due to high temperatures include:

• Adults over 65
• People who don’t exercise regularly
• People who live in tropical climates
• People who work in outdoor settings
• People with cardiovascular disease, such as coronary artery disease or heart failure
• People with chronic conditions such as chronic obstructive pulmonary disease (COPD), kidney disease, or diabetes
• People with disabilities that limit independence and ability to adapt to heat, such as dementia, Parkinson’s disease, or stroke
• Very young children

Medications That Affect Thermoregulation

Some medications can make it harder for your body to adjust to heat, affecting your blood pressure and making you more susceptible to heat stroke.

Medications that may make you more susceptible to low blood pressure in hot environments include:

• Nitroglycerin spray: Used to treat angina (chest pain).
• Beta-blockers: Used to lower high blood pressure and treat heart failure.
• Calcium channel blockers: Used to lower high blood pressure and treat irregular heartbeats and chest pain.
• Angiotensin-converting enzyme (ACE) inhibitors: Used to lower high blood pressure.
• Angiotensin receptor blockers (ARBs): Used to lower high blood pressure and treat heart failure.
• Aspirin: Used to treat pain.
• Plavix (clopidogrel): Used to lower the risk of heart disease and stroke by preventing blood clots.
• Diuretics: Used to help the body eliminate extra fluid, and to treat conditions like heart failure, kidney disease, and high blood pressure.

Tips to Avoid Heat-Related Complications

Whether you’re facing an upcoming heatwave or struggling with a hot environment at home or work, it’s important for your heart health to stay cool. Use the following tips to avoid overheating and heat-related blood pressure complications:

• Avoid drinking alcohol, caffeine, and sugary beverages like soda, which can dehydrate you.
• Avoid intense exercise in the sun; consider swimming for exercise on hot days.
• Eat hydrating, cold foods like watermelon, cucumbers, and salads.
• Avoid preparing meals with your stove or oven, which may further heat up your home.
• Eat small, light meals to reduce the demand for blood flow to your digestive system.
• Keep your home environment cool with air conditioning, fans (a bowl of ice beneath a fan can help you cool off faster), and blackout curtains.
• Know and monitor yourself for the signs of heat exhaustion and heat stroke.
• Stay hydrated by primarily drinking water, but you might also consider electrolyte drinks if you sweat a lot.
• Wear lightweight and breathable clothes; wear a wide-brimmed hat and sunglasses outside.