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‘Extreme Heat Events in India’s Cities: A Framework for Adaptive Action Plans’

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  • Published
    2nd Feb, 2021

Among the most severe consequences of climate change is the global rise in average temperatures, and the resultant heatwaves.

Given the increase in the frequency and intensity of heatwaves, it is essential to prepare and implement hear action plans and to adopt a framework for adaptive action plans.


Among the most severe consequences of climate change is the global rise in average temperatures, and the resultant heatwaves.

Given the increase in the frequency and intensity of heatwaves, it is essential to prepare and implement hear action plans and to adopt a framework for adaptive action plans.


  • Climate change, the long-term alteration of temperature and typical weather patterns, has emerged as a defining challenge of the 21st century.
  • Although it is both naturally induced and anthropogenic in character, climate change’s rapid rate is mostly human-made.
  • Over 150 years of industrialisation, deforestation, fossil fuel use and large-scale agriculture have resulted in record levels of greenhouse gases (GHGs) being emitted into the atmosphere.
  • Burgeoning populations, growing economies, and improved living standards have also meant a considerable rise in the cumulative level of GHG emissions.
  • There is a direct link between the concentration of GHGs in the Earth’s atmosphere and the average global temperature—rising GHG concentration has translated into increasing mean global temperature.
  • Consequently, there will also be impacts on biodiversity and the ecosystem, including species loss and extinction.
  • This is likely to lead to climate-related risks to health, livelihoods, food security, water supply, human security and economic growth.

Important Reports

  • In its Fifth Assessment Report (2013), the United Nations Intergovernmental Panel on Climate Change (IPCC) revealed that between 1880 and 2012, the average global temperature rose by 0.85 percent.
    • The report also stated that a great deal of irreversible damage had already been triggered and most aspects of climate change will persist for centuries, even if emissions are controlled.
  • A 2018 IPCC report concluded that many of the adverse impacts of climate change would come at the 1.5°C mark, including
    • extreme temperatures in most inhabited regions
    • a rise in mean sea level
    • heavy precipitation in many areas
    • the probability of drought and precipitation deficits in some areas


What are Heatwaves?

  • A heatwave refers to surface temperatures being significantly higher than normal for several days at a time.
  • The World Meteorological Organization defines heatwaves as “five or more consecutive days during which the daily maximum temperature surpasses the average maximum temperature by 5°C (9°F) or more”.
  • However, there is no universally accepted definition for heatwaves.
  • Heatwaves are measured relative to the usual weather in an area and the normal temperatures for the season, and so definitional differences are reflective of global climatic variations and the geographically variable nature of heatwaves and their impact.                                           

Different standards on heatwaves

Several countries have adopted their own standards on heatwaves:

  • India: The India Meteorological Department requires that, to be classified as a heatwave, temperatures should reach:
    • at least 40°C in the plains,
    • at least 30°C in the hilly regions and,
    • should reflect an increase of at least 5°C-6°C (or 9°F-10.8°F) above the normal temperature
  • United States: The US National Weather Service defines a heatwave as a spell of “abnormally and uncomfortably hot and unusually humid weather” over two days or more.
  • Denmark: In Denmark, a heatwave occurs when the mean of the highest recorded temperature measured over three consecutive days exceeds 28°C (82.4°F).
  • Australia: In Adelaide, Australia, a heatwave is defined as five straight days with temperatures at or above 35°C (95°F), or three consecutive days at or over 40°C (104°F).

India and Heatwaves

  • India routinely experiences hot summers but, in recent years, several parts of the country have seen abnormally high temperatures—4°C-5°C (39.2°F-41°F) above normal—over several days, being defined as heatwaves.
  • India’s northwest region typically experiences heatwaves between March to June, and in rare cases until July.
  • Heatwaves killed about 6,187 people in India between 2011 and 2018.
  • However, data on heatwave fatalities are not widely available since most cases go unreported and the ambiguity of symptoms may mean that mortality rates are not accurately captured.
  • Urban habitats are more prone to disasters than rural areas—cities have frequently been hit by floods and other calamities and bore the brunt of the COVID-19 pandemic worldwide.
  • Similarly, cities are more vulnerable to heatwaves due to the ‘heat island effect’. Urbanised areas experience higher temperatures due to their built density.

Aren’t ‘heat waves’ and ‘loo’ same?

  • Additionally, during the summer months, north and northwest India also experience the ‘loo’—strong, hot, dry winds that blow during the day and sometimes until late in the evening.
    • On account of its extreme temperature, ranging between 45°C-50°C (115°F-120°F) and very low humidity, the ‘loo’ zaps the human body dry on exposure, leading to fatal heatstroke.
    • However, the ‘loo’ is a normal weather phenomenon in northern India, and heatwaves are considered to occur above this condition not before it.

How ‘urbanization’ is contributing to the phenomenon?

  • Buildings, roads and other infrastructure absorb and re-emit the sun’s heat more than natural landscapes such as forests and water bodies.
  • Urban areas, where such structures are highly concentrated and greenery is limited, become ‘islands’ of higher temperatures in comparison to outlying areas.
  • Consequently, temperatures in urban areas are about 1°F-7°F higher in the daytime and about 2°F-5°F higher in the nighttime than temperatures in outlying areas.
  • India is rapidly urbanising, with many of its cities adding large populations regularly. Indian cities have already experienced the fallout of rising temperatures. In 2015:
    • Hyderabad recorded a temperature of 46°C (114.8°F) on 21 May
    • Delhi was 46.4°C (115.5°F) on 25 May
    • Prayagraj recorded a temperature of 47.8°C (118°F) on 9 June
    • Bhubaneshwar 44°C (111.2°F) on 10 June
  • It was the fifth deadliest heatwave ever recorded, with 2400 death reported across the country that year.
  •  According to the ‘Assessment of Climate Change Over The Indian Region’ report by the Union Ministry of Earth Sciences, India’s average temperature has risen by 0.7°C (33.2°F) between 1901 and 2018 and will rise by 4.4°C (39.9°F) by 2100, while heatwaves will multiply by a factor of two or three and their duration will double compared to the 1976-2005 period.
  • Similar conclusions were made by the McKinsey Global Institute, which predicted that by 2050 India would face many lethal heatwaves—three-day events during which the average daily maximum wet-bulb temperature exceeds the survivability threshold for a healthy human resting in the shade.
    • Scientific literature holds that at 35°C (95°F) wet bulb, a healthy human being can survive by resting in the shade for approximately five hours.

Is the phenomenon limited to India?

Heatwaves are a global phenomenon; around the world, days are getting hotter more frequently. The proportion of the Earth’s surface area that was subjected to scorching summers (significantly higher than the average temperatures) increased from 1 percent between 1951-80 to over 10 percent between 1981-2010.

  • United States: In the US, for instance, the frequency of heatwaves has increased substantially, from an average of two per year during the 1960s to over six per year during the 2010s.
  • England: In England, between 2015 and 2019, over 3,400 people lost their lives on account of extreme temperatures, with nearly 900 extra deaths (deaths above the normal numbers recorded each year) during the 2019 summer heatwaves.
  • Europe: In 2003, a devastating heatwave during Europe’s hottest summer since the sixteenth century killed about 30,000 people across the region.
  • Japan: In 2018, Japan’s weather agency warned of unprecedented levels of threat on account of extreme heat and declared the heatwave sweeping the country as a natural disaster.
  • Africa: While Sub-Saharan Africa has been identified as a heatwave ‘hotspot’, regional governments have not reported such events, but the African continent is as vulnerable to the impacts of heatwaves as elsewhere.

What are health impacts of Heatwaves?

Heatwaves have several health impacts.

  • Dehydration: Heatwaves can cause severe dehydration, acute cerebrovascular accidents and contribute to thrombogenesis (blood clots).
  • Heat cramps: Heat cramps result in edema (swelling) and syncope (fainting), often accompanied by fever below 39°C (102°F).
  • Heat exhaustion and/or heat stroke: Heat exhaustion can cause fatigue, weakness, dizziness, headaches, nausea, vomiting, muscle cramps and sweating. Meanwhile, heat strokes cause the body temperature to rise to 40°C (104°F) or more and can result in delirium, seizures, coma or possible fatality.

Is India taking enough measures?

  • Despite the high incidences of deaths due to heatwaves and the rising number of extreme weather events, India does not recognise heatwaves as a disaster under its Disaster Management Act (2005).
  • AMC’s Heat Action Plan: However, in 2013, the Ahmedabad Municipal Corporation (AMC) implemented the country’s first HAP, developed in the aftermath of the 2010 heatwave that hit the city, with temperatures exceeding 46.8°C (116.2°F) and 1344 people losing their lives.
  • The HAP included four key strategies.
    • Awareness: First, public awareness and community outreach to share information on the risks of heatwaves and dos and don’ts to follow to prevent heat-related deaths and illnesses.
    • Early warning system: Second, to put an early warning system in place to alert citizens about the onset of the heatwave and set inter-agency coordination in motion.
    • Training: Third, to build capacity among healthcare professionals, including paramedical staff and community health staff.
    • Adaptive techniques: Fourth, to launch measures to reduce heat exposure and promote adaptive techniques, such as access to potable drinking water, cooling spaces and night shelters, especially for high-risk populations.
  • NDMA’s guidelines: However, in the wake of the 2015 heatwaves, the National Disaster Management Authority (NDMA) published guidelines on preventing and managing heatwaves.
    • The NDMA urged cities and states to prepare heat action plans (HAPs) that focus on
      • early warning systems
      • training healthcare professionals
      • raising public awareness
      • encouraging collaboration with NGOs and civil society, as a means to tackle heatwaves
    • Several other cities in India have also adopted such strategies.
      • Currently, 30 cities across 11 states facing extreme hot weather conditions have adopted HAPs, including Delhi, Hyderabad, Bhubaneshwar and Nagpur.

What needs to be done?

India must adopt several measures to prepare for and tackle the impacts of heatwaves.

  • Recognition under DM Act: It must recognise heatwaves as a disaster and include it under the Disaster Management Act. This will equip the Centre, states and urban local bodies with statutory powers to enforce orders. It will also give authorities access to revenues that flow from the Act.
  • There are two broad types of responses to disasters:
    • mitigation (the reduction of heatwave sources): Mitigation measures can be more global while adaptation is primarily local.
    • adaptation (adjustment mechanisms to cope with heatwaves): Within adaptation, annual preparatory and operational steps in a city and long-term but local policy-driven design changes should be included.
  • Early warning system: Cities must develop sound early warning systems to inform citizens of a coming heatwave. Additionally, public health information and guidelines should be prepared and made available to all citizens.
  • Special attention to vulnerable people: Special attention must be given to the urban poor and other vulnerable groups.
  • Urban planning: In addition to the short-term steps that need to be taken each year to manage heatwaves, cities must initiate several significant urban planning measures for long-term sustainability.


Given India’s increasing vulnerability to heatwaves, it must first recognize such incidents as a disaster to make national and state disaster assistance available for mitigation efforts. Although the NDMA has issued guidelines on dealing with heatwaves, a national HAP will be extremely beneficial to cities and will “drive a national agenda to embed adaptation planning for rising temperature in our plans and design for space, utilities, infrastructure and industries.”


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