Heatwave in India

Heatwave in India

The intense summer has again brought with the scorching Heat Wave Condition in India. Lets decode the same:

What is heat wave? Which parts of India are affected by it? What time of year do heatwaves strike in India?

A Heat Wave is a period of abnormally high temperatures, more than the normal maximum temperature that occurs during the summer season in the North-Western parts of India.

Typically, heat waves are associated with the north and northwest of India and over coastal Andhra Pradesh, north Odisha and parts of West Bengal. However, there’s been a slight increase in the number of regions in recent years, with more parts of the Himalayan plains, regions north of Andhra Pradesh and Central India also registering more heat waves.

The Indian Meteorological Department (IMD) has given the following criteria for Heat Waves :

  • Heat Wave need not be considered till maximum temperature of a station reaches atleast 40*C for Plains and atleast 30*C for Hilly regions.
  • When actual maximum temperature remains 45*C or more irrespective of normal maximum temperature, heat waves should be declared.
  • Heatwave v/s Severe Heatwave
Normal Temperature of PlaceHeatwave ConditionSevere Heatwave Condition
less than or equal to 40*C Departure from normal is 5*C to 6*CDeparture from normal is 7*C or more
more than 40*C  Departure from normal is 4*C to 5*CDeparture from normal is 6*C or more.

What is making Heatwaves more and more intense?

Higher daily peak temperatures and longer, more intense heat waves are becomingly increasingly frequent globally due to climate change. India too is feeling the impact of climate change in terms of increased instances of heat waves which are more intense in nature with each passing year, and have a devastating impact on human health thereby increasing the number of heat wave casualties.

Studies have also linked an increase in heat waves to more increase in El Nino events, or years marked by an anomalous heating in the Central Pacific Ocean that’s linked to a weakening of the Indian monsoon.

The Indian Ocean temperatures are also rising faster than the other oceans, and this, too, may be reducing moisture over the Indian mainland, thus playing some part in longer stretches of hot days. Deforestation, the heat-island effect, and industrial pollution are also being blamed for exacerbating heat waves.

How do Heatwaves impact us?

Severe heat waves have caused catastrophic crop failures, thousands of deaths from hyperthermia, and widespread power outages due to increased use of air conditioning

The health impacts of Heat Waves typically involve dehydration, heat cramps, heat exhaustion and/or heat stroke. The signs and symptoms are as follows:

  • Heat Cramps: Ederna (swelling) and Syncope (Fainting) generally accompanied by fever below 39*C i.e.102*F.
  • Heat Exhaustion: Fatigue, weakness, dizziness, headache, nausea, vomiting, muscle cramps and sweating.
  • Heat Stoke: Body temperatures of 40*C i.e. 104*F or more along with delirium, seizures or coma. This is a potential fatal condition.

What is India doing to tackle Heatwave disaster?

National Disaster Management Authority is guiding States, in partnership with the India Meteorological Department, to evolve heat action plan protocols.

Better meteorological forecasting can provide an early warning about a coming hot spell during the summer window. This gives the NDMA and the States sufficient opportunity to launch an action protocol: to inform the public as soon as the temperature crosses the threshold fixed by the IMD, advise on precautionary measures, and aid those who are most vulnerable, such as older adults, farm workers and those pursuing outdoor vocations.

Several initiatives by the government, including early-warnings and improved public access to drinking water have been taken by government.

Ahmedabad, for instance, drew up a city-level action plan in the wake of its 46.8°C heatwave of 2010 with support from public health institutions.


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