Context: Climate change is increasing the frequency and intensity of heatwaves, which, in turn, increase the risk and severity of wildfires. This, along with dust, is causing a spike in air pollutants including ozone, a report by the World Meteorological Organization (WMO) has stated.

Heat Waves

• Meaning: It 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.
• Criteria for declaring Heat waves: A region is declared under heat waves when,

o Maximum temperature: Of a station reaches at least 40°C for Plains and at least 30°C for Hilly regions.

o Based on Departure from Normal Heat Wave:

 Departure from normal is 4.5°C to 6.40°C

 Severe Heat Wave: Departure from normal is >6.4°C

o Based on Actual Maximum Temperature Heat Wave:

 When actual maximum temperature ≥ 450°C

 Severe Heat Wave: When actual maximum temperature ≥470°C

o If above criteria met at least in 2 stations in a Meteorological sub-division for at least two consecutive days then it is declared on the second day.

o For coastal regions: When maximum temperature departure is 4.50°C or more from normal, Heat Wave may be described provided actual maximum temperature is 370°C or more.