Why Hot Weather Can Make You Anxious, Irritable and Exhausted
I walked out of my home in London today and, for a moment, it felt less like London and more like Palm Springs in Southern California, where I used to live.
The air felt like an oven.
For a country where most of us have traditionally worried far more about keeping our homes warm than cooling them down, periods of extreme heat can feel particularly relentless. And this summer in England has given us plenty of them.
We tend to think about heat as a physical-health issue: dehydration, sunburn, heat exhaustion and, at the extreme, heatstroke.
But extreme heat affects our mental health too.
If you have found yourself unusually irritable, exhausted, anxious, unable to concentrate or simply desperate for everyone to leave you alone during a heatwave, it may not be your imagination.
There is increasing scientific evidence that high temperatures can affect mood, behaviour, sleep and psychological wellbeing.
Why does extreme heat affect mental health?
Our brains do not operate separately from our bodies.
When the body is struggling to maintain a safe internal temperature, it has to devote resources to doing precisely that. We sweat more, blood flow changes, our heart works harder and we lose fluid. If we become even mildly dehydrated, fatigue and headaches can follow.
At the same time, prolonged discomfort is a stressor.
It becomes harder to sleep. It becomes harder to concentrate. Ordinary frustrations can feel less tolerable. Crowded trains, crying children, a difficult conversation at work or someone moving painfully slowly in front of you at the supermarket can suddenly feel disproportionately irritating.
This is important psychologically.
Research examining temperature and mental health has found associations between higher temperatures and increased mental-health-related hospital attendance, psychological distress and some psychiatric symptoms. Studies have also found associations between heat and suicide risk, although the relationship between temperature and any individual person’s mental health is obviously much more complex than temperature alone.
In other words, heat does not create a psychological problem out of nowhere. It can reduce the resources we have available for managing one.
And that distinction matters.
Does hot weather really make people more aggressive?
There is evidence that it can.
Researchers have been studying the relationship between temperature, aggression and violence for decades. A large systematic review and meta-analysis published in 2024 found an overall association between elevated temperatures and crime and violence, with the evidence particularly apparent for violent crime.
That doesn’t mean that a hot day turns peaceful people into violent people.
Human behaviour is far too complicated for that.
But heat creates conditions that can make emotional regulation more difficult: physical discomfort, dehydration, poor sleep, crowding, frustration and prolonged physiological stress.
When our nervous system is already working hard, our threshold for dealing with additional stress can become lower.
Interestingly, the relationship is not completely linear. Some research suggests that when heat becomes truly extreme, certain types of crime can actually decrease, possibly because people retreat indoors and social interaction falls.
So the evidence is more nuanced than the simplistic statement that “heat causes violence.”
A better way of putting it is this:
As temperatures rise, irritability and aggression can rise too, and our capacity to regulate ourselves may temporarily become more limited.
That is something worth remembering before having an important argument in a 35-degree kitchen.
Heat, anxiety and the nervous system
Extreme heat can also produce bodily sensations that resemble anxiety.
Your heart may beat faster. You may sweat. You can feel weak, nauseous, light-headed or unable to think clearly.
For someone already prone to anxiety or panic, those physical sensations can themselves become frightening.
There is another problem: sleep.
Research consistently shows that hotter temperatures can interfere with both sleep quality and sleep duration. And anyone who has experienced several consecutive nights of inadequate sleep knows what happens next.
We become more emotionally reactive.
Concentration deteriorates. Minor problems feel larger. Patience disappears. Existing anxiety and depression can become harder to manage.
Sometimes what feels like a sudden deterioration in our mental health is partly a profoundly tired and overheated nervous system.
Heat can affect us differently as we age
Extreme heat is not equally demanding on every body.
One of the physiological changes associated with ageing is a gradual reduction in our ability to regulate body temperature effectively. This becomes particularly important in older adulthood.
Older people may sweat less efficiently, have changes in cardiovascular responses to heat and may not experience thirst as strongly. Certain medications and medical conditions can increase vulnerability further.
This is why extreme heat can become much more than an inconvenience for older adults.
What about menopause?
Temperature regulation can also change around menopause.
Hot flushes are not simply a feeling of being hot. Menopause involves changes in the brain’s thermoregulatory system, and research suggests that women experiencing vasomotor symptoms can develop a narrower thermoneutral zone, the range of internal temperature within which the body does not need to start sweating or shivering.
That means relatively small changes in core temperature can sometimes trigger an intense heat-dissipation response.
This does not mean that every postmenopausal woman is unable to regulate her temperature properly. But for women experiencing hot flushes or other vasomotor symptoms, an external heatwave can add another layer of physiological discomfort to a system already sensitive to temperature change.
And prolonged physical discomfort inevitably affects psychological wellbeing.
England is still learning how to live with extreme heat
There is a psychological component to this that I think is often underestimated.
In places where extreme heat has historically been normal, homes, workplaces and daily routines tend to be organised around it.
England largely isn’t.
Many British homes do not have air conditioning. Bedrooms can retain heat overnight. Public transport can become extraordinarily uncomfortable. People continue trying to work, commute, exercise and socialise according to schedules designed for a completely different climate.
There is something psychologically exhausting about having no escape from heat.
If you can cool down for an hour, your nervous system gets a break.
If your bedroom is hot, your living room is hot, the street is hot, the train is hot and your workplace is hot, the stressor becomes continuous.
And sometimes the healthiest response is not to push through it.
How to protect your mental health during extreme heat
Start by treating extreme heat as a genuine physiological stressor rather than something you ought to be able to tolerate through willpower.
Reduce unnecessary demands. If you can rearrange strenuous errands, exercise or a long walk until early morning or evening, do it. Extreme heat is not the ideal time to prove your resilience.
Hydrate regularly. Don’t wait until you feel desperately thirsty. Dehydration can contribute to headaches, fatigue and feeling unwell, all of which make emotional regulation harder.
Protect your sleep. Close blinds or curtains on sun-facing windows during the day. Ventilate when the outside temperature drops. Use a fan if you have one. Even small improvements in overnight temperature can matter if they help you sleep.
Use water to cool your body. A cool shower, damp cloth, cool water on the skin or simply putting your feet in cool water can provide relief.
Find a cooler environment if your home becomes unbearable. A library, cinema, shopping centre, café, museum or other air-conditioned public space may give your body several hours to recover. There is no psychological virtue in remaining inside an dangerously overheated flat.
Lower the emotional temperature too. If you notice yourself becoming unusually irritable, don’t immediately assume that every irritation deserves action. Ask yourself whether you are hungry, dehydrated, exhausted or overheated before beginning a difficult conversation.
Sometimes the best emotional-regulation strategy available is a glass of water and twenty minutes somewhere cool.
Know the difference between feeling miserable and becoming physically unwell
Heat exhaustion can include tiredness, dizziness, headache, nausea or vomiting, excessive sweating, cramps, intense thirst, a high temperature, rapid breathing or heartbeat and irritability.
Heatstroke is a medical emergency.
If someone remains unwell after being cooled and given fluids, becomes confused, loses consciousness, has a seizure or develops other signs of heatstroke, seek urgent medical help.
We should not normalise serious heat illness simply because unusually hot summers are becoming more familiar.
Your brain is part of your body
Perhaps the most important thing to remember during a heatwave is extraordinarily simple:
Mental health is physical health.
We sometimes expect ourselves to maintain exactly the same concentration, patience, productivity and emotional equilibrium regardless of what is happening physiologically.
But a human nervous system is not a machine operating independently of its environment.
Extreme heat places demands on the body. Poor sleep places demands on the brain. Dehydration places demands on both.
So if you feel slower, more irritable, more emotional or less resilient during extreme heat, pay attention to the physical conditions surrounding those feelings before interpreting them as evidence that something has suddenly gone terribly wrong psychologically.
Drink some water.
Get out of the heat if you can.
Postpone the unnecessary argument.
And give your nervous system a chance to cool down.
If you are struggling or having thoughts of suicide, you do not have to manage this alone. In the UK, you can contact Samaritans free, 24 hours a day, on 116 123. If you are in immediate danger, call 999 or go to A&E.
https://www.samaritans.org/how-we-can-help/contact-samaritan/
Evidence and further reading
Research reviews have found associations between elevated ambient temperatures and adverse mental health outcomes, including increased psychological distress, mental-health-related hospital attendance and suicide risk.
A 2024 systematic review and meta-analysis published in Environmental Health Perspectives also found evidence of an association between elevated temperatures and crime and violence, particularly violent crime.
Research into ageing demonstrates that thermoregulatory efficiency declines in older adults, increasing vulnerability during extreme heat.
Research into menopause has shown that reproductive hormonal changes affect thermoregulation and that women experiencing hot flushes can have a narrowed thermoneutral zone, allowing relatively small elevations in core temperature to trigger sweating and vasodilation.
For current UK heat-health guidance, consult the NHS, UK Health Security Agency and Met Office.
Isobel Gardner, CPsych, LMFT is a Chartered and Licensed Clinical and Counselling Psychologist and trauma specialist, and Licensed Marriage and Family Therapist. She offers individual and couples therapy in the Harley Street district of London and online internationally.