Too Hot, Too Cold, Just Right – How Weather Fluctuations Impact Blood Pressure

Last reviewed:
29 Jun 2023,

Medically reviewed by:

Too Hot, Too Cold, Just Right – How Weather Fluctuations Impact Blood Pressure

Do you know how the story goes?

In a famous scene from “Goldilocks and The Three Bears,” a girl named Goldilocks tries three bowls of porridge belonging to the bears. One bowl she finds too hot and one too cold. The third helping of porridge is the right temperature to eat.

All sounds simple. Yet, what’s coined as the “Goldilocks principle” has since been applied to many different disciplines – from statistics to medicine. As it turns out, the principle is relevant when thinking about blood pressure too.

For example:

Does hot weather raise blood pressure? Yes, it can.

Does cold weather raise blood pressure? Yes, absolutely. 

So, in theory, can weather that’s either too hot or too cold pose a health threat to those with hypertension?

Again, the answer is yes. But what if you’re somewhere that’s often too warm or too cool? Where you find yourself sweating or shivering?

Keep reading, because we’ll discuss how cold and hot weather can spike your blood pressure, as well as the right precautions to take.

How Does Hot Weather Raise Blood Pressure – The Background Biology

You may have heard that being in a warm climate is ideal for those with hypertension. There is truth to this – to a point.

Like with most things in life, there is such a thing as too much. Heat is no different.

On average, your blood pressure is likely to be lower in the summer than it is in the winter. The higher temperatures cause blood vessels to dilate to radiate heat. In turn, this makes it easier to pump blood around the body and blood pressure levels reduce.

Sounds good so far for people with hypertension, doesn’t it?

Alas, we did warn there’s a catch. And that catch is dehydration.

Dehydration May Be Subtle, But It Can Also Be a Killer

When you’re in a hot environment, your blood vessels have to work to maintain homeostasis by expanding. But if that expansion happens too fast it can cause blood pressure to drop. Your heart reacts to such a sudden drop by pumping harder and at a more rapid rate. Can you guess what happens then?

Your blood pressure spikes. Not good.

The other significant piece of the puzzle here is hydration. When you’re not able to replace fluids at the same rate you lose them through sweat, breath, and urination, this causes a fluid imbalance. Blood volume then decreases. As a result, your tissues and organs don’t receive enough oxygen or nutrients to function normally.

The different stages of dehydration can cause your blood pressure to fluctuate. In the initial stages, your blood pressure may drop as blood volume decreases. But this can quickly yo-yo and your blood pressure goes up. Here’s why:

  • A hormone called vasopressin is key in regulating blood pressure. When blood volume is low or sodium levels in the blood are high after losing too much fluid, vasopressin is secreted.
  • High amounts of vasopressin cause the blood vessels to narrow, raising blood pressure.

With this in mind, those with hypertension or cardiovascular disease need to be vigilant.

Avoid dehydration by keeping your fluids topped up. The NHS recommends water or diluted squash as good options. Caffeine and alcohol won’t suffice as they have the opposite effect.

The simplest test to check how well hydrated you are?

If your pee is a pale yellow or clear color, you’re doing OK. If it’s a darker yellow or light orange, there’s your warning to sign to drink more water.

“Endless Record Heat” Warnings in 2023 Pose Extra Risk of High Blood Pressure

Increased blood pressure from dehydration may become more prevalent as temperatures soar around the world.

Here are a few of the worrying weather reports and forecasts this year:

  • ‘Endless record heat’ in Asia as highest April temperatures recorded – The Guardian
  • These are the places most at risk from record-breaking heat waves as the planet warms – CNN
  • State of the climate: Growing El Niño threatens more extreme heat in 2023Carbon Brief

It’s impossible to ignore the growing trend. Unprecedented extremes of heat are occurring in various countries and continents.

Climate experts predict that the Earth’s average temperature will increase by 4° C this century, based on greenhouse gas emissions continuing to rise at the same rate.

While the implications of this change are wide-ranging, let’s stay focused on the topic of blood pressure. If you have hypertension, make sure you drink plenty of water during the warmer months of the year.

Drinking the same amount as you do in the winter won’t be enough if you are perspiring more in the heat.

Two litres of water (eight 8oz glasses) is the typical daily recommendation. This goes up to at least two and a half litres (ten 8oz glasses) during warmer weather.

Why Cold Weather Is Also a Blood Pressure Risk Factor

So, we’ve established that hot weather does raise blood pressure in certain people. What about the cold?

The blood vessels in and near the skin react to cold temperatures by constricting to not lose too much heat. It’s a protective biological feature. But there’s a downside too – constricted blood vessels can result in higher blood pressure.

The evidence?

Check out this long-term study of how blood pressure is affected by weather fluctuations. Published in the science journal, Hypertension, the researchers monitored the blood pressure of over 16,000 people across 40 years. They mapped each person’s clinic visit for their blood pressure measurement to the weather conditions on the day of the visit.

Around 35% of the participants were classified as “temperature sensitive.” These people were significantly affected by cold weather. They had a higher risk of mortality. They also had higher systolic blood pressure in follow-up visits than the non-temperature-sensitive participants.

The Winter Lifestyle Effect

Let’s not forget how changes in lifestyle factors during cold weather can impact blood pressure too.

People tend to consume more calories and eat less healthily during the winter. Plus, people often engage in less physical activity and prefer to stay warm inside.

Another factor is sunlight exposure. With fewer hours of light during the coolest months of the year, less serotonin gets released. Sometimes nicknamed the “feel-good hormone,” sunlight triggers the release of serotonin. How do people adjust to less serotonin from the sun?

Eating carbohydrate-rich foods seems to be one workaround. Carb intake has been shown to boost serotonin levels. Some people take this too far though. They may overconsume carb-dense foods such as chips, biscuits, and chocolate in the winter to boost their mood. But over the long term, they feel worse.

Colder temperatures. Less exercise. An inclination to eat more salty and sugary foods. All things considered, those with hypertension need to take extra care during the winter to keep their blood pressure in check.

Don’t Chance It – Track Your Blood Pressure 24/7 in Cold and Hot Weather

We’ve established that hot and cold weather can both pose risks to people with elevated blood pressure.

Rather than guessing or only measuring your blood pressure a couple of times a week, there is a more practical alternative.

Aktiia’s easy 24/7 blood pressure monitoring tool saves you a lot of time and a lot of uncertainty. Worn as a lightweight bracelet around your wrist, Aktiia tracks your blood pressure day and night with automatic measurements.

It takes away the hassle and the guesswork. You can share readings with your doctor or family members if you wish, so relevant people are in-the-know.

Curious to find out more? Learn about Aktiia here.

Disclaimer: If you are concerned about your blood pressure, it is best to speak to your doctor. They can advise on the best way to manage your blood pressure.


Blood pressure: Is it affected by cold weather? March 2022 –

Fluid imbalance, July 2016 –

Can Dehydration Affect Your Blood Pressure? January 2020 –

(NHS) Dehydration, November 2022 –

Blood Pressure Response to Patterns of Weather Fluctuations and Effect on Mortality, May 2013 –

Seasonal variation in food intake, physical activity, and body weight in a predominantly overweight population, December 2005 –

How Wintertime Affects Our Eating Habits, January 2021 –

Brain Serotonin, Carbohydrate-Craving, Obesity and Depression, November 1995 –

Medically Reviewed

dr jay shah photo

Renowned cardiologist, physician leader, and angel investor.

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