Print Friendly, PDF & Email

What are heat waves?

Topics Covered: Important Geophysical phenomena such as earthquakes, Tsunami, Volcanic activity, cyclone etc.

What are heat waves?


As per the India Meteorological Department (IMD), Heat wave conditions very likely in isolated pockets over Rajasthan, Vidarbha and interior Tamil Nadu.

  • The warning comes after maximum temperatures of more than 40 degrees Celsius were recorded recently in most pockets.

What is a heatwave?

The IMD says heatwave is considered when the maximum temperature of a station touches at least 40 degrees Celsius or more for plains, 37 degrees Celsius or more for coastal regions and at least 30 degrees Celsius or more for hilly regions.

What are the criteria?

Heatwave is declared when the departure from normal temperature is by 4.5 to 6.4 degrees Celsius and a severe heatwave is when the departure from normal is more than 6.4 degrees Celsius.

  • For plains, based on actuals maximum temperature, IMD considers heatwave when actual maximum temperature is more than 45 degrees Celsius and severe heatwave when it is more than 47 degrees Celsius.

Reasons why India is experiencing more heat waves are:

  1. Magnified effect of paved and concrete surfaces in urban areas and a lack of tree cover.
  2. Urban heat island effects can make ambient temperatures feel 3 to 4 degrees more than what they are.
  3. More heat waves were expected as globally temperatures had risen by an average 0.8 degrees in the past 100 years. Night-time temperatures are rising too.
  4. Higher daily peak temperatures and longer, more intense heat waves are becomingly increasingly frequent globally due to climate change.
  5. High intensity of UV rays in medium-high heat wave zone.
  6. Combination of exceptional heat stress and a predominantly rural population makes India vulnerable to heat waves.

Way ahead for India- How India should deal with heat waves?

  1. Identifying heat hot-spots through appropriate tracking of meteorological data and promoting timely development and implementation of local Heat Action Plans with strategic inter-agency co-ordination, and a response which targets the most vulnerable groups.
  2. Review of existing occupational health standards, labour laws and sectoral regulations for worker safety in relation to climatic conditions.
  3. Policy intervention and coordination across three sectors health, water and power is necessary.
  4. Promotion of traditional adaptation practices, such as staying indoors and wearing comfortable clothes.
  5. Popularisation of simple design features such as shaded windows, underground water storage tanks and insulating housing materials.
  6. Advance implementation of local Heat Action Plans, plus effective inter-agency coordination is a vital response which the government can deploy in order to protect vulnerable groups.


Prelims Link:

  1. When is a heat wave declared?
  2. Criteria?
  3. Difference between heatwave and super heatwave?
  4. What is IMD?

Mains Link:

Examine the adverse impacts caused by heat waves and how India should deal with it?

Sources: PIB.