A heatwave occurs when the temperature of a region rises above its average temperature. This extreme weather condition persists for almost 2-7 days or sometimes even longer. In India the extreme heat wave starts typically between the months of March and July. During this period the temperature soars above 45°C.

When the temperature rises above the typical range or more for at least five days in a row, meteorologists claim it as a heatwave. National weather agencies in various nations establish their own criteria based on local climate trends. Let’s explore more about this natural phenomenon, its impact, causes and preventive measures.

What is a Heatwave?

A heatwave is an extended period of extremely hot weather that is much hotter than the typical temperatures for a certain area and season. It can also be accompanied by high humidity. This extreme weather condition can last anywhere from a few days to several weeks and is not just an uncomfortable day. In different parts of India the wave occurs mainly between March and June. Heatwaves can occur in any geographical region including deserts, tropical areas and even polar regions. In recent decades they have been recorded in South Asia, Europe, UAE and Australia.

Effects of Heatwave on Our Health

Heatwaves have an adverse effect on the human body beyond physical discomfort. One of the most prevalent health effects of heatwave is heat exhaustion, which happens when the body loses too much salt and water through perspiration. Tiredness, nausea, and headaches are among the most common symptoms of heat exhaustion.

Heat stroke is a dangerous form of heat-related sickness in which the natural capability of our body to control its temperature stops working. This condition can result in organ failure, brain damage, and even death if treatment is not received.
Loss of fluids from the human body in the form of sweat due to prolonged heat leads to dehydration, which can impact various functions in the human body including blood pressure, kidneys and brain.
Respiratory problems can happen due to the poor air quality during heatwaves: the concentrations of pollutants and ground-level ozone in heatwaves are high. This can lead to asthma attacks and other respiratory issues.
Higher levels of heat are also related to poor emotional or cognitive functions causing extreme anxiety, despair, anger and sleep difficulties.

The impact of heatwaves is not just restricted to human health but also reflects on the environment, economy and society. It speeds up the vaporisation of rivers and other water bodies, causing drought-like situations impacting drinking water supply and agriculture. Heatwaves also cause frequent forest fires destroying the ecosystem and the natural habitat of wildlife. Prolonged heat may reduce the soil ability to absorb water and support plant growth leading to desertification of land.

Factors Causing Heatwave

Deforestation can lead to high temperatures as trees form a natural air-conditioning system by releasing water vapours. Extensive deforestation causes intense heat.

Heatwaves are becoming more common, strong, and prolonged due to human-caused climate change. Burning the fossil fuels releases harmful gases like methane and CO2 that traps the heat in the Earth's atmosphere. Due to this the average temperature of earth rises. According to research, earlier heatwaves used to happen once in 50 years. But in recent times, this duration has come down to 10 years.

Natural climate variations such as El Niño can impact weather causing extreme heatwaves. This climate pattern contributes to heating the ocean surface, rising temperatures of many regions.

Urban heat island effect is the impact of heat trapped in urban regions made of concrete, asphalt and buildings. These structures trap heat contributing to heatwaves. Lack of trees and green spaces reduces natural cooling thus affecting the temperature of the place.

Preventive Measures

Although preventing the effect of heatwaves is not completely possible, we can use some preventive measures to reduce its impact on lives such as adapting energy-efficient practices and technologies to lower overall energy demand. Planting more trees and raising awareness about the impact of deforestation and excessive urbanisation. Also, educating people about the ways they can contribute to reducing global warming.

DOs and DON’Ts

DOs	DON’Ts
Increase water intake.	Keep drinking plenty of water, even if you're not thirsty.
Stay indoors specially during the peak heat hours i.e., from 11am to 4pm	Avoid working out outside while the temperature is at its highest.
Wear light cotton and breathable clothes	Avoid dressing in tight or dark clothing. Children and pets should not be left in cars.
Apply sunscreen when going outside.	Avoid eating large, heated meals.
Look after the elderly and children. Keep pets indoors with water.	Don’t ignore early signs of heart stress