Hot summer days are great for spending time outside, but if you have high or low blood pressure, warmer weather can pose some risks to your health. Understanding how heat affects your body — and knowing how to respond — can help you stay safe and comfortable all season long.
What blood pressure means
Your blood pressure is the force of blood pushing against your artery walls. It’s measured using two key numbers:
- Systolic pressure (top number), which reflects the pressure when your heart beats
- Diastolic pressure (bottom number), which reflects the pressure when your heart rests between beats
A normal reading is usually around 120/80. High blood pressure typically starts at 130/80 or above, while low blood pressure is anything below 90/60. Both high and low blood pressure can cause symptoms, especially when combined with heat or medication.
Why blood pressure changes in summer
Your body regulates temperature by widening or narrowing your blood vessels. In cold weather, the vessels narrow to conserve heat, which can increase blood pressure. In warm weather, they widen to release heat, which reduces resistance in the bloodstream and can lead to lower blood pressure. For most people, these changes are mild. But if your blood pressure is already low, or you take medication that affects your circulation, hot weather can increase your risk of dizziness, fatigue, or fainting.
When low blood pressure becomes concerning
Low blood pressure usually isn’t considered a serious health threat unless it’s accompanied by symptoms such as fatigue, nausea, confusion, dizziness, fainting, neck or back pain, headaches, blurred vision, or heart palpitations.
How heat can affect blood pressure
Even though warm weather often causes blood pressure to drop, people with high blood pressure are not always in the clear. Dehydration is a major concern. And when you sweat and don’t drink enough fluids, your blood becomes more concentrated. This can make your heart have to work harder and cause your blood pressure to rise instead of fall.
How medications can amplify the effects of heat
Some blood pressure medications can increase your sensitivity to heat or affect how your body regulates temperature. Two common examples are:
- Beta blockers, which slow your heart rate and can reduce blood flow to the skin and make it harder for your body to cool down
- Diuretics, which lower blood pressure by removing excess fluid but can lead to dehydration or increased sun sensitivity
If you take these or other blood pressure medications, have a conversation with your doctor about how to avoid potentially risky blood pressure changes during the summer months.
How to stay safe in hot weather
If you have low or high blood pressure, it’s important to monitor it regularly. The American Heart Association recommends getting an automatic blood pressure monitor with a cuff that fits around your upper arm so you can check your readings at home.
If you’re on medication for high blood pressure, you should be aware of the warning signs of low blood pressure, which can be triggered by heat. Watch for symptoms like dizziness, nausea, or confusion, and move to a cooler place if they occur.
To avoid heat-related blood pressure issues, stay in air-conditioned spaces when possible, limit outdoor activity to early morning or evening hours, wear breathable clothing, drink plenty of water, and know the signs of heat illness.
Small changes can make a big difference
Hot weather can affect your blood pressure in ways you might not notice right away. That’s why it helps to understand how heat and humidity can affect your body. By making a few easy changes, you can protect your health and still enjoy everything summer has to offer.