What is a Heat Wave?

A Heat Wave is an episode of extraordinarily high temperatures exceeding the average maximum temperature in North-Western India during the summer. Heat waves are most common between March and June, although they might last into July in rare situations. Extreme temperatures and the ensuing climatic conditions harm people living in these areas because they produce physiological stress, which can lead to mortality. Long periods of high day and nighttime temperatures impose cumulative physiological stress on the human body, exacerbating the world’s leading causes of death, such as respiratory and cardiovascular illness, diabetes mellitus, and kidney disease.

Heatwaves can severely impact considerable populations in a short period, resulting in excess mortality and cascading socioeconomic effects (e.g., reduced work capacity and labour output). They can also lead to a loss of healthcare delivery capacity, as power outages, common during heatwaves, impair healthcare institutions, transportation, and water infrastructure.

Heat waves are common in India from March through June, and in extreme situations, they can last until July. Five to six heat wave episodes occur yearly in the country’s northern areas. Single incidents can last weeks, emerge in succession, and affect a vast population. Bihar, Jharkhand, Gangetic West Bengal, Odisha, Punjab, Haryana, Chandigarh & Delhi, Rajasthan, Maharashtra, West Madhya Pradesh, and Gujarat were all afflicted by severe heat waves since 2016.

Heat waves across India

An early heatwave warning has been issued by the Indian Meteorological Department with projections for higher-than-normal temperatures between March and May, following the country’s hottest February since 1901. The Intergovernmental Panel on Climate Change reports provides solid evidence that the frequency and intensity of heat waves are expected to increase in the future with every degree of further warming to the world’s climate.

Since the pre-industrial period, the average temperature at the Earth’s surface has risen by around 1°C, a rate unmatched in human history. While the temperature shift may not appear rapid, it has resulted in 17 of the 18 warmest years on record occurring in the twenty-first century. Between March and April 2022, India experienced disastrous heat waves, with temperatures rising 8°C above usual for the time of year. In early summer 2022, the country suffered five times the amount of heat wave days that it did in the same season in 2021. The severity and size of heat waves in India in 2023 are unknown. However, warning indicators are there.

A heat wave is declared when the highest temperature at a station exceeds 40°C for Plains and 30°C for Hilly areas.

a) Departure from Normal Heat Wave: The deviation from normal is 4.50°C to 6.40°C. Severe Heat Wave: The variation from normal is more significant than 6.40 degrees Celsius.

b) Heat Wave Based on Actual Maximum Temperature: When the maximum temperature is 450°C Severe Heat Wave: The maximum temperature is 47 degrees Celsius.

It was declared on the second day if at least two stations in a Meteorological sub-division matched the conditions above for at least two consecutive days.

How do Heat Waves affect people?

Blood vessels dilate as the body heats up. This lowers blood pressure and makes the heart work harder to circulate blood throughout the body. As blood vessels become leaky, this might cause subtle symptoms such as itching, heat rash, or swollen feet. At the same time, sweating causes fluid and salt loss, and the equilibrium between them in the body shifts.

Heat exhaustion can result from this, paired with low blood pressure. Among the symptoms are: dizziness, nausea, fainting, disorientation, muscle cramps, headaches, intense sweat, and exhaustion. When blood pressure falls too low, the risk of a heart attack increases.

Effects of Extreme Heat

Extreme heat can cause dehydration, heat exhaustion, and heatstroke in the worst-case scenario. Heat exhaustion is usually not dangerous if a person can cool down within 30 minutes. However, it must be handled as an emergency if it progresses to heatstroke. Children, the elderly, and persons with chronic health issues such as diabetes and heart disease are particularly vulnerable to heat exhaustion and heatstroke.

Hot days are also associated with an increased risk of several other conditions not considered heat-related, such as kidney problems, skin infections, and pre-term birth in pregnant women. In reality, heatstroke, heat exhaustion, and dehydration account for only a less portion of the total health hazards associated with days of intense heat.

People who are elderly or have long-term diseases, such as heart disease, may be less able to cope with the burden that heats places on the body. Diabetes causes the body to lose water more quickly, and some disease complications might affect blood vessels and sweating ability. Children and individuals with limited mobility may be particularly vulnerable. People suffering from brain illnesses, such as dementia, may either be ignorant of the heat or unable to do something about it. Homeless people will also be more exposed to the sun. Those who live on the top floors will also experience increased temperatures.

What measures may be taken to prepare for heat waves?

We also need to make our communities less vulnerable to the already-existing effects of climate change. Many localities have programs in place to address climate-related health concerns. There are techniques that we know are effective for dealing with the health risks connected with excessive heat:

1. Heatwave early warning systems can keep people safe by communicating heat wave threats and recommending preventive measures. These warning systems are far less expensive than treating and managing heat sickness.

2. Heat alerts serve as a wake-up call for cities and counties to take preventive measures, such as creating cooling centres where people can seek relief from the heat. Air conditioning is the most effective way to defend against high heat and is a critical health resource for vulnerable groups.

3. Staying hydrated and avoiding intense outdoor exertion during heat alerts can help protect people from the dangers of excessive heat.

4. Making public drinking fountains, swimming pools, and spray pads easily accessible can help keep people cool during excessive heat.

5. Building codes and landscaping standards can be updated to improve energy efficiency. It also enhances structures’ ability to guard against extreme heat events. For example, green roofs (with plant cover) and strategically placed shade trees can reduce internal temperatures and enhance building energy efficiency.

6. Urban forests, which include street trees and woodland areas, can help to reduce urban heat islands by up to 9°F.

What can be concluded?

Climate change is causing higher daily peak temperatures and longer, more intense heat waves to become more common worldwide. India, too, is facing the effects of climate change in the form of increased heat waves, which are becoming more intense each year and have a terrible impact on human health, increasing the number of heat wave casualties. Heat waves require dry and clear conditions to thrive. Hot, dry air from the Middle East enters India and combines with increased solar heating from a lack of clouds, creating circumstances conducive to heat waves.

In recent months, there has been a lack of winter storms in that section of the world, known as western disturbances, which would ordinarily disrupt any growing warm spells. Heatwaves have various significant repercussions on human health, ecosystems, agriculture, water and energy supply, and vital economic sectors.

Also Read: What Is Heatflation?