One minute you're sitting at your desk. The next, heat moves through your chest and neck. Your face feels warm. Your heart beats a little faster. Maybe you start sweating.

Then, a few minutes later, it's over.

Hot flashes are one of the most common symptoms of perimenopause and menopause. They can happen during the day or at night, when they're often called night sweats. And while they can feel sudden and strangely intense, there is a reason behind them.

First, what exactly is a hot flash?

A hot flash is a sudden feeling of warmth, usually around the face, neck and upper body.

You may also notice:

• sweating
• flushed skin
• a faster heartbeat
• chills afterwards
• anxiety or a feeling of being suddenly unsettled

A single episode can last from a few minutes to longer, depending on the person.

Hot flashes are also called vasomotor symptoms, because changes in the body's blood vessels are part of the response. They are very common during the menopause transition. Around 80% of women experience hot flashes or night sweats at some point. But there is no single way to experience them.

Some women have a few mild episodes. Others wake several times a night, change their clothes and start the next day already exhausted. Both are normal variations of the same transition.

It starts in your brain

Your body has its own temperature control system. One of the key players is the hypothalamus, a small area in the brain that helps regulate body temperature. Think of it as your internal thermostat.

Normally, the hypothalamus allows your body temperature to move within a fairly broad range without you noticing much. During perimenopause, changing hormone levels can make this system more sensitive [4]. The range becomes narrower—what physiology research describes as a narrowed thermoneutral zone [4].

A small change in body temperature that your brain previously ignored may now be interpreted as: too warm.

Your body responds by trying to cool you down.

Blood vessels close to the skin widen. Blood flow increases. You sweat. Your heart rate can rise.

And suddenly, you're very aware of your temperature.

Then your body settles again.

This is why a hot flash can feel as though it comes out of nowhere. Your body isn't randomly overheating. It's responding to a change in how your brain is regulating temperature.

Why can they start before menopause?

This is an important one. You don't need to have reached menopause to experience hot flashes. They can begin during perimenopause, sometimes years before your final period.

That's because perimenopause isn't a smooth decline in hormones. Estrogen can rise and fall. Your cycles can change. Some months may feel completely normal, while the next brings a different combination of sleep disruption, temperature changes, mood shifts or cycle changes. This is one reason perimenopause can feel unpredictable. Your body is responding to hormonal changes as they happen.

Why are my hot flashes different from hers?

Because there is no standard perimenopause experience. One woman may have one hot flash every few weeks. Another may have several every day.

Some notice them mostly at night. Others experience them while working, exercising or sitting in a meeting.

Research has identified several factors associated with more frequent or severe vasomotor symptoms, including smoking, higher body weight and the stage of the menopause transition. But these factors don't explain every woman's experience.

Your pattern is your own. And that can be useful information.

What can trigger a hot flash?

You may notice that certain situations make hot flashes more likely or more intense. Commonly reported triggers include:

Alcohol
Caffeine
Heat
Spicy food
Stress
Smoking
Exercise in a warm environment

But there is an important caveat: the evidence around individual triggers is mixed. Your trigger list doesn't need to look like anyone else's. Instead of cutting out everything you enjoy, try paying attention.

For a week or two, note when a hot flash happens and what came before it. What did you drink? How did you sleep? Were you stressed? Had you exercised? Were you somewhere warm?

You might start to see a pattern. The goal isn't to follow a long list of rules. It's to understand your own body a little better.

It's not just about the heat

The hot flash itself may last only a few minutes. The effect can last much longer. This is particularly true at night. A night sweat wakes you up. You throw off the duvet, open a window or change your clothes. Then you have to fall asleep again. 

Do that several times a week and the problem is no longer just temperature. It's sleep. And disrupted sleep can affect your energy, concentration and mood the following day. This is why we shouldn't look at hot flashes in isolation. Sometimes the most difficult part isn't the heat. It's what happens afterwards.

Are hot flashes a warning sign?

This is where things get interesting.

Recent research has looked at whether vasomotor symptoms are associated with cardiovascular and cognitive health [1] [2] [3].

A pooled analysis published in the American Journal of Obstetrics & Gynecology found associations between vasomotor symptom severity and cardiovascular disease. A systematic review and meta-analysis in Maturitas examined the broader evidence on vasomotor symptoms and cardiovascular risk. And Harvard Health (2025) has discussed the newer understanding of hot flashes, cardiovascular health and cognitive health in the context of the menopause transition.

But there is an important distinction: an association does not mean that hot flashes cause heart disease or cognitive decline.

Much of this research is observational. Other factors, including age, blood pressure, cholesterol, diabetes, physical activity, body weight and sleep, can influence both hot flashes and long-term health.

As Harvard Health (2025) notes, the relationship is particularly nuanced. The timing, severity and persistence of symptoms matter, as does overall cardiovascular health. So a hot flash in your 40s or early 50s isn't a reason to panic. It can be a reason to pay attention.

Perimenopause is a useful moment to look at the bigger picture: blood pressure, cholesterol, blood sugar, movement, nutrition, sleep and stress. Not because your hot flashes mean something is wrong. Because this stage of life is a good time to understand your health more fully.

And sleep matters more than you might think

There may be another piece of the puzzle. Hot flashes can disrupt sleep, and poor or fragmented sleep is itself associated with cardiovascular and cognitive health. That means some of the longer-term health associations seen in research may be partly connected to what happens during those broken nights.

This is one reason persistent night sweats deserve attention. You don't have to simply accept years of poor sleep as part of getting older.

What can actually help?

Start with your environment. Especially at night. A few small changes can make hot flashes easier to manage:

• Keep your bedroom cool.
• Choose lightweight sleepwear.
• Use breathable bedding.
• Keep a fan nearby.
• Keep water next to the bed.
• Try a lighter duvet.

If you notice a particular trigger, experiment with it.

If evening alcohol seems to make your nights worse, try a few alcohol-free evenings.

If afternoon caffeine seems connected to nighttime symptoms, move your last coffee earlier.

One change at a time gives you a better idea of what actually makes a difference.

And if hot flashes are affecting your sleep, work or quality of life, there are medical treatments worth discussing too.

You don't have to just put up with them

Hot flashes are common. That doesn't mean you have to live with severe symptoms without support. Hormone therapy is an effective treatment for bothersome menopausal vasomotor symptoms and may be appropriate for many women after an individual discussion of benefits and risks with a healthcare professional.

For women who don't want or can't use hormone therapy, other evidence-based options are available, including menopause-specific cognitive behavioural therapy and certain non-hormonal medicines. The right option depends on your symptoms, medical history and preferences.

This is one of those areas where a conversation with your doctor or menopause specialist can be much more useful than trying to figure everything out from a symptom list.

How long will this last?

The frustrating answer is: it varies. The JAMA/SWAN study found that menopausal vasomotor symptoms lasted a median of 7.4 years overall, with symptoms continuing for a median of 4.5 years after the final menstrual period [5]. Women whose frequent symptoms started earlier in the transition tended to experience them for longer. But a median is not a prediction.

Some women experience hot flashes for a much shorter time. Others experience them for longer. There isn't a countdown clock inside your body. And you don't need to compare your timeline with someone else's.

When should you speak to a doctor?

If hot flashes are disrupting your sleep, work, relationships or quality of life, that's enough reason to ask for help. You can also speak with a healthcare professional if:

• your symptoms are severe or becoming more frequent
• you're regularly waking drenched in sweat
• your sleep is suffering
• you're struggling with daytime fatigue or concentration
• something about your symptoms feels unusual for you

And pay particular attention to timing.

If hot flashes first appear many years after menopause, or continue well into later life, it's worth discussing them with a doctor rather than automatically assuming they're related to menopause. Harvard Health (2025) recommends investigating unusual timing, particularly when symptoms appear anew or persist 10 or more years after menopause [1].

The bottom line

A hot flash isn't your body malfunctioning. It's your brain's temperature control system responding differently as hormones change. Sometimes it's barely noticeable. Sometimes it wakes you at 3 a.m. and leaves you wondering what just happened.

Both experiences can be part of perimenopause. The more useful question isn't simply How do I stop this? It's: What is my body telling me?

Notice the pattern. Protect your sleep. Understand your triggers. Know what treatment options exist. And use this stage as an opportunity to pay attention to your wider health, too. Perimenopause isn't something you have to decode alone. Understand what's changing. Then decide what support makes sense for you.

FAQ

What causes hot flashes? Changing ovarian hormones during perimenopause and menopause can make the hypothalamus, the part of the brain involved in temperature regulation, more sensitive to small changes in body temperature. Your body then responds by releasing heat through sweating and increased blood flow to the skin.

Can you have hot flashes during perimenopause? Yes. Hot flashes can begin years before your final period. You don't need to have reached menopause to experience them.

How long does a hot flash last? A single episode commonly lasts a few minutes, although experiences vary. The overall period during which someone experiences hot flashes can last several years. The JAMA/SWAN study found a median duration of 7.4 years overall [5].

Why are my hot flashes worse at night? Night sweats can wake you from sleep, and the resulting sleep disruption can make the experience particularly difficult. Your room temperature, bedding, alcohol, caffeine and stress may also influence your symptoms.

Can caffeine cause hot flashes? Caffeine is a commonly reported trigger, but not everyone responds to it in the same way. Rather than automatically cutting it out, pay attention to whether you notice a consistent connection.

Are hot flashes bad for your heart? Not necessarily. Research has found associations between more severe vasomotor symptoms and cardiovascular health, but this does not prove that hot flashes cause heart disease. Other factors such as blood pressure, cholesterol, diabetes, physical activity and sleep also matter.

Can hot flashes affect your brain? Research is exploring associations between severe vasomotor symptoms, sleep disruption and cognitive health. The relationship is complex, and current observational research does not show that hot flashes themselves cause cognitive decline.

What can I do when a hot flash starts? Try cooling your environment, removing a layer, using a fan or drinking cool water. Over time, tracking your symptoms can also help you identify personal triggers.

Do I need treatment for hot flashes? Not necessarily. If your symptoms are mild and manageable, you may not need treatment. If they are affecting your sleep or quality of life, there are effective treatment options worth discussing with a healthcare professional.

When are hot flashes not normal? Hot flashes are common during perimenopause and menopause. However, new hot flashes many years after menopause or symptoms that persist well into later life should be discussed with a healthcare professional to check whether another cause could be involved.

Can you experience chills during perimenopause? Yes. Alongside hot flashes, you can also experience sudden chills during perimenopause. Hormonal fluctuations can affect how your body regulates temperature. You may feel hot one moment and start shivering shortly after. Chills can also have other causes. If they persist or feel unusual, it’s a good idea to speak with your doctor.

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This article is for informational purposes only and is not medical advice. If you have concerns about your symptoms, speak with a qualified healthcare professional.

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Sources

• [1] Harvard Health. Hot flashes, cardiovascular health and cognitive health in the menopause transition. 2025.

• [2] American Journal of Obstetrics & Gynecology. Pooled analysis of the association between vasomotor symptom severity and cardiovascular disease.

• [3] Maturitas. Vasomotor symptoms and cardiovascular risk: systematic review and meta-analysis.

• [4] Physiology research on the narrowed thermoneutral zone in menopausal hot flashes.

• [5] JAMA/SWAN Study. Duration of menopausal vasomotor symptoms over the menopause transition.