5 things that happen to your body when mercury climbs above 45 degrees | Health - Hindustan Times

5 things that happen to your body when mercury climbs above 45 degrees

By, New Delhi
May 23, 2023 08:59 PM IST

Scorching summer days are here and killer heatwaves have left many parts of India sizzling hot. This is how the body reacts when mercury goes beyond 45 degrees.

The killer heatwaves have left many parts of north India sizzling hot in the past few days. With temperature moving past 45 degrees, it's becoming challenging for the body to adjust to the extreme weather condition. To cope up with the extreme heat, our body activates its in-built cooling system of sweating, the heart beats faster, and blood vessels expand allowing more blood to flow through them. The body can also become susceptible to heat exhaustion and heat stress which could cause symptoms like dizziness, fatigue, nausea, and muscle cramps. In rare cases, extreme heat can result in multiple organ failure. (Also read: 7 healthy ways to lose weight in summer season)

With the rise in mercury levels, sweat becomes our ally, blood vessels expand like never before, and our hearts race to beat the heat,(Rahul Raut/HT file photo)
With the rise in mercury levels, sweat becomes our ally, blood vessels expand like never before, and our hearts race to beat the heat,(Rahul Raut/HT file photo)

"Roasting summer days are here and when the scorching heat of summer pushes the mercury above 45 degrees Celsius (113 degrees Fahrenheit), our bodies undergo several intriguing changes. The intense heat takes a toll on our physiology, triggering a range of responses that help us adapt and survive in these extreme conditions. With the rise in mercury levels, sweat becomes our ally, blood vessels expand like never before, and our hearts race to beat the heat," Dr Parinita Kaur, Senior Consultant- Internal Medicine, Aakash Healthcare, New Delhi told HT Digital in an interview.

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Dr Kaur goes on to explain how our bodies adapt when faced with scorching temperatures above 45 degrees.

1. Increased sweating

As the mercury soars, our body activates its built-in cooling system — sweating. When the temperature exceeds 45 degrees, sweat glands work overtime to release perspiration, which evaporates on the skin, creating a cooling effect. Sweating helps regulate body temperature and prevents overheating, but it also leads to water and electrolyte loss. It becomes crucial to replenish fluids and maintain proper hydration to avoid dehydration and related health complications.

2. Blood vessel expansion

In response to extreme heat, our blood vessels expand in a process known as vasodilation. When the temperature rises above 45 degrees, blood vessels near the skin's surface widen, allowing more blood to flow through them. This expansion facilitates heat dissipation and helps regulate body temperature. However, the dilation of blood vessels can sometimes cause a drop in blood pressure, leading to dizziness or fainting. It is essential to stay hydrated and take breaks in cooler environments to support cardiovascular health during extreme heat.

3. Increased heart rate

When faced with scorching temperatures above 45 degrees, our heart rate tends to rise. The body perceives high temperatures as a stressor and reacts by increasing cardiac output to deliver oxygen and nutrients to the cells more efficiently. The heart beats faster to maintain an adequate blood supply throughout the body, supporting the cooling mechanisms and maintaining vital organ function. However, individuals with pre-existing heart conditions should take extra precautions during extreme heat to prevent overexertion.

4. Skin changes and sunburn

Extended exposure to temperatures above 45 degrees can lead to various skin-related issues. The scorching heat can cause the skin to become dry, irritated, and more susceptible to sunburn. The ultraviolet (UV) radiation from the sun becomes more intense, increasing the risk of sunburn and long-term skin damage. It is crucial to protect the skin by applying sunscreen, wearing protective clothing, and seeking shade during peak sunlight hours to prevent harmful effects on the skin.

5. Heat exhaustion and heatstroke

Excessive heat can push the body's temperature-regulating mechanisms to their limits, leading to heat-related illnesses like heat exhaustion and heatstroke. Heat exhaustion occurs when the body loses significant amounts of water and electrolytes through excessive sweating, resulting in symptoms such as dizziness, fatigue, nausea, and muscle cramps. If left untreated, heat exhaustion can progress to heatstroke, a life-threatening condition characterized by a body temperature above 40 degrees Celsius (104 degrees Fahrenheit) and severe organ dysfunction. Heatstroke requires immediate medical attention to prevent irreversible damage.


Dr. Sarat Sahoo, Senior Consultant – Internal Medicine, Apollo 24|7, and Apollo Hospitals, Sector-26, Noida shares with HT Digital the health conditions extreme heat can put us at risk of.

1. Dehydration: During periods of intense heat, dehydration is one of the main concerns. Your body produces more perspiration when the temperature rises above 45 degrees in an effort to stay cool. So, dehydration may result from the increased fluid loss. Symptoms of dehydration include light-headedness, dry mouth, weariness, and a reduction in urine production. Drinking plenty of fluids, particularly water, and avoiding alcoholic or sweetened beverages will help you keep hydrated.

2. Cardiovascular stress: The cardiovascular system can experience severe stress from high temperatures. When the body is exposed to intense heat, blood vessels expand to help the body release heat, which lowers blood pressure. As the body tries to adjust, this may cause an elevated heart rate. People who already have heart disease, or other cardiovascular issues such as hypertension, are more at risk. During intense heat, it's important to stay in cool spaces and limit physical activity.

3. Respiratory distress: Chronic obstructive pulmonary disease (COPD) and asthma are two respiratory disorders that might get worse in extremely hot weather. The airways can get irritated by hot air, which can cause bronchospasms and make breathing difficult. Additionally, air pollution levels may increase during heatwaves, aggravating respiratory problems even further. People who have respiratory issues need to take extra care, like staying inside in air-conditioned spaces and taking their medications as directed.


Dr Ajay Agarwal, Director & HOD - Internal Medicine, Fortis Hospital Noida says heatstroke or heatwave can be deadly and one must take precautionary measures. "Those at greatest risk for heat-related illness typically include infants and children up to four years of age, people 65 years of age and older, people who are overweight, and people who are ill or on certain medications," says Dr Agarwal.

Stay hydrated: Drink plenty of water throughout the day, even if you don't feel thirsty. If exercising, take frequent breaks for hydration and cooling.

Avoid going out during the hottest parts of the day: Try to stay indoors during peak sun hours, typically from 10 a.m. to 4 p.m.

Dress appropriately: Wear loose-fitting, light-coloured clothing made of breathable fabrics like cotton.

Use sunscreen: Apply sunscreen with a high SPF to protect your skin from the sun's harmful rays.

Cool off: Take cool showers or baths, use fans or air conditioning, and use cool compresses to reduce your body temperature.

Keep an eye on others: Check in on older adults, young children, and people with medical conditions to make sure they are staying cool and hydrated.

Avoid strenuous activities: Limit physical activities that can increase your body temperature, especially during the hottest parts of the day.

If you or someone you know experiences symptoms of heatstroke, such as a high body temperature, confusion, dizziness, nausea, or a rapid heartbeat, seek medical attention immediately.

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