In News: Many districts in Rajasthan, Haryana, Uttar Pradesh, Madhya Pradesh have been posting temperatures over 45 degrees Celsius or five degrees above what is normal.
What is Heat wave ?
- Heat wave is considered if the 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 a heat wave, the above criteria should be met at least in 2 stations in a Meteorological subdivision for at least two consecutive days and it will be declared on the second day.
Impact of Heat Wave Warning
| Warning | Impact | Suggested Actions |
| Nil | Comfortable temperatures | No cautionary action required |
| Heat wave conditions at district level, likely to persist for 2 days | Heat is tolerable for general public but moderate health concern for vulnerable people e.g. infants, elderly, people with chronic diseases. | Avoid heat exposure |
| i. Severe heat wave conditions likely to persist for 2 days. ii. With varied severity, heat wave is likely to persist for 4 days or more. | Increased likelihood of heat illness symptoms in people who are either exposed to sun for a prolonged period or doing heavy work. High health concern for vulnerable people e.g. infants, elderly, people with chronic diseases. | Avoid heat exposure– keep cool. Avoid dehydration
|
| i. Severe heat wave likely to persist for more than 2 days. ii. Total number of heat/severe heat wave days likely to exceed 6 days. | Very high likelihood of developing heat illness and heat stroke in all ages.
| Extreme care needed for vulnerable people. |
