What is Heat Wave?

  • According to the Indian Meteorological Department (IMD) on May 29, 2019 heat wave conditions were in most parts with Severe Heat wave in isolated pockets over Vidarbha; heat wave in many parts with severe heat wave in isolated pockets over West Rajasthan; Heat Wave to Severe Heat Wave in isolated pockets over East Uttar Pradesh; Heat wave conditions in some parts over Marathwada, Telangana and Madhya Pradesh and in isolated pockets over northern parts of North Interior Karnataka, Madhya Maharashtra, East Rajasthan and Haryana, Chandigarh & Delhi.
  • The highest maximum temperature of 48°C was recorded at Chandrapur (Vidarbha) on May 29.
  • Ganganagar (West Rajasthan) & Khujraho (East Madhya Pradesh) recorded the maximum temperature of 47.2°C (Annexure 3) on May 30.

What is Heat Wave?

  • Heat wave is considered if maximum temperature of a station reaches at least 40°C or more for Plains, 37°C
    or more for coastal stations and at least 30°C or more for Hilly regions.
  • Following criteria are used to declare heat wave:
    a) Based on Departure from Normal:
    Heat Wave: Departure from normal is 4.5°C to 6.4°C
    Severe Heat Wave: Departure from normal is >6.4°C
    b) Based on Actual Maximum Temperature (for plains only)
    Heat Wave: When actual maximum temperature ≥ 45°C
    Severe Heat Wave: When actual maximum temperature ≥47°C
  • To declare heat wave, the above criteria should be met at least in 2 stations in a Meteorological sub-division
    for at least two consecutive days and it will be declared on the second day.
Photo credit: IMD

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