Can high humidity affect brain function?

Yes. Extreme heat and humidity can cause temporary brain effects like brain fog, irritability, and trouble concentrating. Dehydration and heat stress can reduce oxygen delivery to the brain and increase mental fatigue.

How does heat affect people with high blood pressure?

Extreme heat can strain the heart and cause dehydration or electrolyte imbalances. Dehydration can lower blood volume and trigger blood pressure changes. People taking blood pressure medications should be especially cautious in hot weather.

How can I stay safe during hot, humid weather?

Stay safe by drinking plenty of fluids, avoiding alcohol and caffeine, limiting outdoor activity during peak heat, resting in shaded or air-conditioned spaces, and wearing lightweight clothing. Air conditioning is the best protection during extreme heat.

The Surprising Way Humidity and Heat Can Trigger Stroke Risk

Q: Does humidity affect blood pressure and stroke risk?

Yes. Hot, humid weather can increase stress on the heart and blood vessels. High humidity makes it harder for the body to cool itself, which can lead to dehydration, higher blood pressure changes, and increased cardiovascular strain.

Q: How does heat and humidity affect the body?

Heat causes the body to sweat and increase blood flow to the skin to stay cool. High humidity slows sweat evaporation, making it harder to regulate body temperature. This can lead to dehydration, heat exhaustion, or heat stroke. Heat stroke is a medical emergency that occurs when body temperature rises above 104°F.

Q: Does hot weather increase stroke risk?

Hot weather may increase stroke risk, especially ischemic stroke caused by blood clots blocking blood flow to the brain. Research shows high temperatures can temporarily increase stroke risk because heat can cause dehydration, thicker blood, and greater clot risk, especially in people with existing risk factors.

The Surprising Way Humidity and Heat Can Trigger Stroke Risk

Does humidity affect blood pressure and stroke risk?

Hot, humid weather is more than uncomfortable; it can place real stress on the body. In regions like south Louisiana, where summer heat index values have reached as high as 120°F, understanding how heat and humidity affect blood pressure and stroke risk is especially important.

How does heat and humidity affect the body?

When temperatures rise, your body cools itself by sweating and increasing blood flow to the skin. Humidity interferes with this process by slowing the evaporation of sweat, the body’s primary cooling mechanism. As a result, your core temperature can rise, increasing the risk of heat-related illness.

Common heat-related conditions include:

Dehydration
Heat exhaustion
Heat stroke

According to the American Stroke Association, heat stroke occurs when the body overheats and core temperature exceeds 104°F. This is a medical emergency.

Does high humidity affect the brain?

Extreme heat and humidity can also affect brain function. Studies suggest high humidity may reduce cognitive performance, sometimes described as “brain fog,” and may contribute to irritability, impulsivity and difficulty concentrating.

Dehydration and heat stress can reduce the efficiency of oxygen delivery to the brain. In addition, elevated levels of the stress hormone cortisol during extreme heat may increase anxiety and mental fatigue.

Does hot weather increase stroke risk?

It’s important to distinguish between heat stroke and acute ischemic stroke:

Heat stroke results from dangerously high body temperature.
Acute ischemic stroke occurs when a blood vessel supplying the brain becomes blocked by a clot, depriving brain tissue of oxygen.

According to the American Stroke Association, heat stroke is when your body overheats, and core body temperature rises to more than 104° F. Acute ischemic stroke is when a blood vessel to the brain bursts or is blocked by a clot. Brain cells die from the lack of blood and oxygen.

Emerging research suggests that high temperatures may further increase stroke risk. A 2024 study in JAMA Network Open, a medical journal published by the American Medical Association, found that high temperatures may leave people more vulnerable to acute ischemic stroke.

Heat can:

Cause dehydration
Increase blood viscosity (thickness)
Raise the likelihood of blood clots

These changes can increase vulnerability in individuals already at risk for stroke.

Heat, humidity and high blood pressure

Hot and humid weather can significantly affect blood pressure and cardiovascular health.

According to the Centers for Disease Control and Prevention, extreme heat increases strain on the heart and may contribute to dehydration, electrolyte imbalances and blood clots, all of which can increase hospitalizations for cardiovascular conditions.

Dehydration can:

Lower blood pressure due to reduced blood volume
Trigger stress hormone release, potentially causing blood pressure spikes

People with high blood pressure should take extra precautions, especially those taking medications such as diuretics or beta blockers, which may increase sensitivity to heat.

How can I stay safe in hot, humid weather?

The Louisiana Department of Health recommends remembering three key words during extreme heat: water, rest, and shade.

Protect yourself by:

Drinking plenty of fluids, and don’t wait until you feel thirsty
Consuming 16–32 ounces of water per hour during heavy activity
Avoiding alcohol, caffeine and sugary drinks
Limiting outdoor activity to early morning or evening hours
Taking frequent breaks in shaded or air-conditioned spaces
Wearing lightweight, loose-fitting, light-colored clothing
Using sunscreen, a wide-brimmed hat and sunglasses

Air conditioning is the most effective protection against extreme heat. If your home is not air-conditioned, spend time each day in a cooling center, library or other climate-controlled environment. Even a few hours can help lower your body temperature and reduce health risks.

Learn more about Kim Lee, MD.

8 Ways to Stop a Stroke Before a Stroke Stops You

Learn the warning signs to look out for if someone is having a stroke and things you can you do to prevent a stroke from happening. Also, learn why programs such as Ochsner's ASSERT telemedicine program, located at Ochsner Medical Center in New Orleans, can be so valuable to patients who find themselves experiencing a stroke.

Top Symptoms of a Stroke You Must Know

Take our quiz to learn your risk of a stroke.

Can High Blood Pressure Cause Stroke? What You Should Know

High blood pressure, also called hypertension, often has no obvious symptoms. Yet over time, it can quietly damage the heart, brain, and kidneys without a person realizing it. The good news is that blood pressure can be managed with the help of your physician.