From brain to gut, what 45 degrees Celsius temperature does to your body

Everywhere in India, there’s one topic on people’s minds and lips — the unbearable heat. The rising mercury is being felt across the country, and people are struggling to cope with the heat and sweat.

In Delhi, the condition is particularly bad, with Monday (May 18) becoming the hottest day in the month so far. Additionally, India’s weatherman has predicted that the temperature is only set to become worse over the next few days.

As Delhiites brace for even harsher heat, we take a closer look at what happens to the body in such weather conditions. Can our body withstand the heat, or does it wither?

The heat is on in the Capital

In India’s Capital, Delhi, the temperatures are soaring, leaving people to sizzle and sweat it out. On Monday (May 18), the primary weather centre recorded a maximum temperature of 43.4 degrees Celsius, making it the hottest day this month so far.

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And the India Meteorological Department (IMD) has warned that temperatures in the national capital could climb to 44-45 degrees Celsius amid continuing heatwave conditions across northwest India. In fact, the IMD has issued a yellow heatwave alert for Delhi and NCR for Tuesday, cautioning residents about excessive heat, rising heat stress, and hot, dry winds through the week.

Weather experts note that the current heat is a result of the absence of active western disturbances and pre-monsoon rainfall activity over north India. Mahesh Palawat, vice president at Skymet Weather, was quoted by the Hindustan Times as saying that dry and hot winds from western and northwestern regions are pushing temperatures higher across Delhi, and that no major relief is expected in the coming days.

Moreover, Palawat explained to New Indian Express that the northwesterly winds travelling across the Thar Desert region have become intensely dry before reaching Delhi, trapping heat near the surface and worsening conditions across the city.

People cover themselves on a hot summer day in New Delhi, Tuesday, May 19, 2026. Delhi experienced a warm Tuesday morning as the minimum temperature settled at 28.2 degrees Celsius, while the India Meteorological Department (IMD) issued a 'yellow' alert for heatwave conditions, with isolated places in the city likely to reel under intense heat during the day. PTI

The extreme heat and the body

As the temperature keeps rising in Delhi and northern India, the main concern is what happens to the human body in this kind of heat.

Doctors note that temperatures in the 40s can wreak havoc on the human body, from the brain to the gut, to even the skin. Research from the University of Roehampton shows that once the mercury crosses the 35-degree Celsius mark, breathing becomes faster and the heart rate increases. At around 40 degrees Celsius, the body works much harder to stay cool, increasing its energy use by nearly 35 per cent. While core body temperature remains stable for a while, prolonged exposure can be dangerous.

Dr Sharat S Kolke MD, DNB (Medicine) noted, “At temperatures below 40°C heat exhaustion with weakness, dizziness, nausea, syncope, and headaches can occur. When the temperatures go beyond 40°C, heat stroke with central nervous system dysfunction, including delusions, seizures or fits, or coma can occur.

Medical experts note that extreme heat causes the blood vessels to open up. This lowers your blood pressure and makes your heart work harder to push the blood around the body.

One could also experience a heat stroke, which is deadly. A heat stroke could cause the brain to swell, leading to headaches and even seizures in more extreme cases. Victims also experience an altered level of consciousness, including confusion, delirium, hallucinations, agitation, and even unconsciousness.

Heat stroke also affects the renal system. A heat stroke decreases urine output and causes a condition known as acute tubular necrosis, in which the kidneys fail to receive enough oxygenated blood to support proper function. If untreated, heat stroke can eventually cause the kidneys to fail.

The extreme heat can also spell trouble for your skin. As Dr Richa Jotwani, a dermatologist based in Mumbai explained, "As the UV rays of the sun are at a very high level, it can cause one's skin to age faster. Moreover, it impacts the skin at a very cellular level."

She also noted that extreme heat affects the skin's barrier, which could cause bacterial and fungal rashes. "Watch out for more infections, prickly heat, and even acne," she told Firstpost.com.

Dr Jotwani further observed that very high temperatures could also result in sun sensitivity among certain individuals.

A pedestrian with his head covered in a cloth walks across a marketplace on a hot summer afternoon in New Delhi. AFP

Doctors also note that rising temperatures could impact one’s digestive system. Christopher Minson, a professor of physiology at the University of Oregon, explained in an Outsideonline report that whenever one exerts physically, blood flow to non-essential organs, like the gut, is reduced. The result is that your gut, which is normally rich with blood, is put under significant duress and its function declines. “It becomes harder to digest and absorb nutrients, and the chances of nausea and general GI-distress rise dramatically.”

Extreme heat can also affect fertility and the reproductive system. A study has shown that very high temperatures can cause fertility issues in men. Similarly, in women, excessive heat causes hormonal imbalances in women, leading to irregular periods, poor egg quality, and implantation difficulties in those trying to conceive.

Expectant mothers also have to be aware of the impact of extreme heat on their bodies. One study revealed that pregnant women exposed to extreme temperatures (both high and low) during gestation faced a 2.26-fold increased risk of preterm birth compared to those experiencing optimal ranges around 25-27 degrees Celsius. There are other risks too, note experts.

Dr Kolke added, “Elderly people, young children, people with underlying heart conditions, high blood pressure, obese people and people on certain medicines like diuretics and BP medicines are more prone to heat related complications.”

The 45-degree heat and its impact on mental health

The scorching heat doesn’t just affect the body physiologically, but also psychologically. One could feel sluggish or irritable, or one might have a more serious exacerbation of an underlying mental health condition.

JoAnna Leuck, MD, Associate Dean for Academic Affairs at Burnett School of Medicine at Texas Christian University, was quoted as telling VeryWellMind.com, “Extreme heat is a stressor both on the body and the mind. Individuals with mental health issues can have more extreme reactions to stress, which can cause their symptoms to worsen.”

Dr Nathan Carroll, Chief Resident Psychiatrist, Jersey Shore University Medical Centre, also found that a person feeling the effects of extreme heat might not be sleeping as well, so along with being fatigued, they may feel more irritable, angry, or anxious during the day.”

Labourers use a cart to transport aluminium pipes at a market on a hot summer day in New Delhi. Reuters

Staying safe in this heat

With the temperature showing no signs of reducing, it’s imperative to know how to stay healthy in this heat.

Most medical experts have cautioned against stepping out in the heat. Stay indoors and avoid direct exposure to the sun, as it leads to exposure and causes the body to work overtime to maintain a nominal body temperature. Dr Jotwani recommends that people should avoid being outside in the hours between 10 am and 2 pm.

Stay hydrated. Drink lots of water and add water-heavy fruits and vegetables to one’s diet. Carry a bottle of ORS when stepping out in the heat. Make sure to rehydrate the body every two hours.

If one has to step out, don’t forget to apply sunscreen. This will protect your skin from the sun’s harmful rays.

Regularly monitor children, the elderly, and those with chronic conditions.

Also, remember to exercise earlier in the day, when temperatures are cooler, and sunlight is not as powerful.

With inputs from agencies