Feeling hot-headed this summer? You’re not alone. Science explains why

Have you ever noticed your mood shifting on days when the heat feels almost unbearable? The smallest things start to feel irritating and even routine tasks seem oddly exhausting. As extreme heat tightens its grip across continents, experts say this is not just discomfort, but has a measurable impact on the human mind and body. According to reports, with temperatures crossing 45 degrees in parts of India and heatwave conditions intensifying across north-west and central regions, multiple cities have already been pushed into extreme stress zones, with some even ranking among the hottest places in the world on a given day. Experts are also warning that the effects go beyond physical health. According to Dr Sonal Agarwal, who is a psychologist at Navayuga Kanya Vidyalaya, Lucknow, “Intense heat increases irritability because it raises overall stress and lowers emotional control. When people feel uncomfortable for long periods, their patience naturally decreases.”

Research adds that high temperatures can impair attention, memory and emotional regulation by increasing stress hormones and disrupting sleep.With forecasts pointing to above-normal temperatures globally, heat is increasingly becoming not just an environmental issue, but a mental health stress test for millions.

Heatwave 2026: India in the grip of extreme temperatures

India is currently experiencing one of the most intense phases of the 2026 heat season, with large parts of the country locked in persistent and widespread heatwave conditions.The India Meteorological Department (IMD) has issued heat alerts across multiple states, warning that the situation is likely to continue for several days with little immediate relief in sight.

IMD has placed several regions under orange and yellow alerts, signalling both severe and moderate heatwave risk. Among the worst-affected regions, Uttar Pradesh, central India and Maharashtra’s Vidarbha belt have emerged as key hotspots. Temperatures have consistently climbed above 45 degrees in several districts, with Banda recording as high as 47.4 degrees.Delhi has also been placed on alert as authorities implement heat action plans, including measures to protect outdoor workers and schoolchildren during peak afternoon hours.This simultaneous rise across regions points to a larger atmospheric pattern affecting both north and central India, with clear skies, dry winds and the absence of rainfall allowing temperatures to build steadily throughout the day.

Why is this heatwave so severe?

The current heatwave is not an isolated weather spike but the result of multiple reinforcing climate drivers acting together at the same time. Scientists and global agencies point to a combination of oceanic warming patterns, large-scale atmospheric conditions and long-term climate change trends that are amplifying heat intensity across regions like India.

One of the key factors is the likely return of El Niño conditions. According to the World Meteorological Organization (WMO), climate models show growing confidence in the development of El Niño as sea surface temperatures in the equatorial Pacific continue to rise.The WMO’s Global Seasonal Climate Update also warns of ‘a nearly global dominance of above-normal land surface temperatures’ over the coming months, suggesting that warmer-than-usual conditions are not limited to one region but are part of a broader global pattern.For India, this becomes particularly critical because El Niño events are often linked with weaker monsoon performance. The IMD has already forecast a below-normal southwest monsoon for 2026, marking the first such projection in three years. Reduced rainfall not only impacts agriculture but also allows land surfaces to heat up more quickly, intensifying and prolonging heatwave conditions.Adding to this is the effect of climate change, which is steadily raising baseline temperatures and increasing the frequency of extreme heat events. Reports also highlight atmospheric ‘heat dome’ conditions, where high-pressure systems trap hot air over large regions, preventing it from dispersing and leading to sustained, extreme surface heating.

Heat stress on body and brain: From heatstroke to brain fog

Extreme heat does not just make people uncomfortable; it pushes the human body and brain toward their biological limits. Scientists describe heat stress as a cascading failure of the body’s cooling system, which begins long before symptoms become visible and can quickly escalate into medical emergencies if exposure continues.At the core of this process is thermoregulation. The human body normally maintains a stable internal temperature through sweating and blood circulation. However, research shows that when a combination of heat and humidity crosses what is known as the ‘wet-bulb temperature’ threshold of around 35°C, the body can no longer cool itself effectively.

Sweat stops evaporating and core temperature begins to rise uncontrollably, creating life-threatening conditions.This progression often moves from dehydration to heat exhaustion and then heatstroke. Early symptoms include fatigue, dizziness and excessive sweating, but can rapidly escalate into organ failure or loss of consciousness. Experts observe that heat also places heavy strain on the heart and kidneys as the body diverts blood flow to regulate temperature, while dehydration reduces circulation efficiency and increases cardiovascular stress. Certain groups are especially vulnerable. Dr Allder in The Independent, highlights that elderly people, children and outdoor workers face the highest risk.Dr Akanksha Rastogi, who works with Children First in Gurgaon explains that children are among the most affected during extreme heatwaves, as rising temperatures disrupt their daily activity, energy balance and emotional regulation. “In children, heat affects the overall system because the body uses more resources to regulate temperature and manage mild distress. Since their regulatory system is still developing, prolonged heat exposure combined with dehydration and reduced outdoor play can have a stronger impact.”“Children naturally have high energy levels, but during heatwaves they are unable to go out and play as much, which means their energy is not utilised properly. This often leads to irritability and crankiness. The disruption also affects sleep cycles, making children more restless and emotionally sensitive,” she added. Scientists explain that this happens due to multiple overlapping mechanisms. Heat increases cortisol, the body’s primary stress hormone, while also disrupting serotonin levels that regulate mood and emotional balance. This behavioural shift is not just observational but rooted in psychological response to prolonged discomfort.Dr Jyoti Mishra, Senior Consultant – Psychology at Apollo Spectra Hospital, Delhi, explains, “During the extreme conditions, the body is already working harder in order to regulate the temperature and this physical discomfort can directly impact emotional control. Heat can also disturb sleep, increase fatigue, reduce concentration and low patience levels as well. In psychological context, when the body feels stressed or uncomfortable for a longer duration, the brain becomes quite more reactive and less tolerant for every trigger.”At the same time, cognitive functions begin to slow down. Studies show declines in attention, memory retention and decision-making ability as temperatures rise, even among young and healthy individuals.This creates what many researchers describe as ‘mental fatigue’ or heat-induced brain fog. People report feeling sluggish, less motivated, easily distracted and emotionally drained.Combined with poor sleep during hot nights, this can significantly reduce productivity and emotional resilience.Dr Sana Sood, a counselling psychologist and rehabilitation counsellor, says: “Repeated exposure to heat can cause our sympathetic nervous system to remain relatively active over time, much like background noise that you become oblivious to but it’s still present. This may result in diminished emotional resilience, mental exhaustion, and irritation.”

How can a heatwave affect our sleep cycle?

The impact of extreme heat does not end when the sun goes down. In fact, scientists say some of the most damaging effects begin at night, when the body struggles to recover from daytime heat exposure. Normally, core body temperature drops during sleep, helping the brain transition into deeper stages of rest such as REM sleep. But during heatwaves, this natural cooling process is disrupted.Research cited by BBC science shows that ideal sleep temperatures lie roughly between 19°C and 21°C. When nighttime temperatures remain high, the body finds it harder to lose heat, leading to shallow, broken sleep and frequent awakenings.

This also affects melatonin production, the hormone that regulates sleep cycles, reducing sleep quality and delaying recovery. The result is next-day fatigue, poor concentration and lower productivity, even in healthy individuals.Police records and urban studies have shown spikes in assaults, road rage and even homicide rates during heat periods, suggesting that heat acts as a behavioural stress trigger, BBC reported.Scientists explain this through a combination of physiological and psychological strain. Heat reduces self-control by affecting cognitive function, while simultaneously increasing irritability through stress responses in the brain.Socio-economic factors further intensify the impact. Communities with limited access to cooling, overcrowded housing or outdoor labour exposure experience higher levels of stress during heatwaves.Experts also warn that the impact of heat is not always immediate and can build over time.Dr Prashant Goyal, Senior Consultant – Psychiatry at Sri Balaji Action Medical Institute, Delhi, says, “Repeated exposure to heatwaves can also create a cumulative response to stress. Even if people do not consciously connect their mood along with the weather, the body also continues to experience heat as a physical stressor.”

Heat as an economic shock

Extreme heat is no longer just a seasonal inconvenience; it is increasingly acting as a silent economic shock that slows productivity, disrupts labour systems and deepens inequality across societies. As temperatures rise beyond safe working thresholds, entire sectors begin to feel the strain, from factories and construction sites to schools and informal workplaces.Industrial output is particularly vulnerable. Heat exposure reduces efficiency in labour-intensive sectors such as textiles, garment manufacturing, steel production and construction, where workers often operate in non-air-conditioned environments. Reports from India’s heat action planning and government advisories highlight how midday hours between 1pm and 4pm are increasingly being avoided or rescheduled to prevent heat-related illness. The impact extends into human capital as well. High temperatures reduce cognitive performance, affecting attention, memory and decision-making. This translates into lower workplace productivity and weaker educational outcomes. Students writing exams or studying in overheated environments show reduced concentration and lower performance.

Government response and heat action plans

As extreme heatwaves become more frequent and intense, governments across India are increasingly relying on early warning systems and structured heat action plans to reduce casualties and manage public risk.In Delhi, the Heat Action Plan 2026 has been activated as temperatures remain consistently above seasonal averages. Authorities have introduced targeted interventions such as ensuring uninterrupted water and power supply, increasing access to cooling resources and distributing oral rehydration solution (ORS) in schools to prevent dehydration among children.

Officials have also been directed to restrict outdoor work during peak heat hours, particularly between 1 pm and 4 pm, when sun exposure is most dangerous.At the workplace level, construction and outdoor labour schedules are being adjusted in several regions, with mandatory rest breaks and modified shift timings becoming more common. These measures are aimed at reducing heat exposure among workers who are most at risk of heat exhaustion and heatstroke.

Survival guide: How people are beating the heat

As heatwaves intensify, everyday survival strategies have become essential for managing both physical comfort and health risks. One of the most important defences is hydration. Health experts consistently recommend regular water intake even before thirst begins. ORS, along with water-rich foods such as cucumber, watermelon, strawberries and citrus fruits, help replenish both fluids and essential salts lost through sweating.Clothing choices also play a critical role. Loose-fitting, light-coloured cotton clothes are widely recommended as they allow better air circulation and reduce heat absorption. Staying in shaded or cooler indoor environments during peak sunlight hours is strongly advised, particularly between late morning and late afternoon when temperatures are at their highest.

Simple cooling techniques can also make a significant difference. Using fans, taking a cold shower and applying wet cloths to the neck or forehead help lower body temperature through evaporation. In homes without air conditioners, keeping curtains closed during the day and improving airflow during cooler hours can reduce indoor heat buildup.Experts recommend avoiding strenuous outdoor exercise during peak heat hours and shifting walks or workouts to early mornings or late evenings when temperatures are comparatively lower. For those who must work outdoors, regular breaks, shade access and hydration become critical safety measures.

The bigger picture: A hotter, more uncertain future ahead

The current heatwave is not an isolated weather event but part of a larger, accelerating global pattern. Across continents, extreme temperatures are becoming more frequent and more intense. Europe, for instance, is warming at nearly twice the global average.Long-term projections offer little immediate relief. Even if countries meet existing commitments under the 2015 Paris Agreement, the United Nations Environment Programme estimates global temperatures could still rise by at least 2.5°C by the end of the century. Experts describe heat as a ‘silent killer’ because its impact is often undercounted and indirect. As seen in recent years, deaths linked to extreme heat frequently go underreported. The debate ahead is increasingly about adaptation versus mitigation. While adaptation measures are becoming essential for survival, scientists emphasize that they are not enough on their own. The root cause remains continued greenhouse gas emissions and without addressing this problem, adaptation will only remain a short-term measure.In essence, the growing intensity of heatwaves is reshaping how millions live, work and survive. What was once considered seasonal discomfort is now emerging as one of the defining climate challenges of this century.