Preliminary   > Disaster Management   >   Disasters   >   Disaster risk reduction

Why in news?

  • Many areas of India are likely to experience severe to very severe heatwave conditions.

What is a heatwave and when is it declared?

  • Heatwaves occur over India between March and June.
  • Meteorologists declare a heatwave event when the maximum (day) temperature for a location in the plains crosses 40 degrees Celsius.
  • Over the hills, the threshold temperature is 30 degrees Celsius.
  • When the day temperature jumps by 4 to 5 degrees above the normal maximum temperature of a location, it is declared as a heatwave.
  • Alternatively, any location where maximum temperature crosses 45 degrees or shows a departure of over 6 degrees from normal, it is a severe heatwave condition.

How long can a heatwave spell last?

  • A heatwave spell generally lasts for a minimum of four days but can extend up to seven or ten days.
  • Heatwaves are common over the Core Heatwave Zone (CHZ) — Rajasthan, Punjab, Haryana, Chandigarh, Delhi, West Madhya Pradesh, Uttar Pradesh, Chhattisgarh, Orissa, Vidarbha in Maharashtra, parts of Gangetic West Bengal, Coastal Andhra Pradesh and Telangana, as categorised by India Meteorological Department.
  • Factors like Western Disturbances which cause rainfall over northern India can reduce the impact of heat waves.

Prelims Question

Consider the following statements regarding Heat waves:
1.In India, heat waves are declared when the maximum temperature jumps by 4 to 5 degrees above normal.
2.Heatwaves occur in India between March and June 
Choose the correct statements from the codes given below:
(a)1 only
(b)2 only
(c)Both 1 and 2
(d)Neither 1 nor 2

Answer to the Prelims Question