A heat wave is a period of abnormally high temperatures, more than the normal maximum temperature that occurs during the summer season in the North-Western and South Central parts of India.
Heat waves typically occur between March and June, and in some rare cases even extend till July.
Higher daily peak temperatures and longer, more intense heat waves are becoming increasingly frequent globally due to climate change.
Heat wave is considered if maximum temperature of a station reaches ≥ 40°C or more for Plains and ≥ 30°C or
more for Hilly regions.
Based on Deviation/Departure from Normal Heat Wave:
If deviation from normal is 4.5°C to 6.4°C, it is normal Heat Wave.
If deviation from normal is >6.4°C, it is severe Heat Wave.
If above criteria is met at least in 2 stations in a Meteorological sub-division for at least 2 consecutive days. The health impacts of Heat Waves typically involve dehydration, heat cramps, heat exhaustion and/or heat stroke.
It also causes heat cramps, fatigue, weakness, dizziness, headache, nausea, vomiting, muscle cramps and sweating.
The extreme temperatures and resultant atmospheric conditions adversely affect people living in these regions as they cause physiological stress, sometimes resulting in death.Adequate replacement of salt and water, although excessive water intake alone should be avoided because of the risk of dilutional Hyponatremia.Heat waves can and do cause roads and highways to buckle and melt, water lines to burst, and power transformers to detonate, causing fires. Heat waves can also damage rail roads, such as buckling and kinking rails, which can lead to slower traffic, delays, and even cancellations of service when rails are too dangerous to traverse by trains.
Heat waves often lead to electricity spikes due to increased air conditioning use, which can create power outages, exacerbating the problem. In addition to physical stress, excessive heat causes psychological stress, to a degree which affects performance, and is also associated with an increase in violent crime. High temperatures are associated with increased conflict both at the interpersonal level and at the societal level. In every society, crime rates go up when temperatures go up, particularly violent crimes such as assault, murder, and rape. Furthermore, in politically unstable countries, high temperatures are an aggravating factor that lead toward civil wars.
Recently, the India Meteorological Department (IMD) has forecasted the “heatwave to severe heatwave conditions” over northwest, central and adjoining peninsular India along with heavy rain over northeast India. Many parts of coastal Andhra Pradesh, Odisha and Maharashtra have also observed increase in temperatures above 42°C, triggering heatwave conditions. The heat wave has been observed due to dry northwesterly winds prevailing over northwest and central India.
While climate change does have a strong link with the occurrence of extreme weather events, it isn’t the cause for extreme weather events. Episodes of heat waves are growing more common as climate change intensifies. Therefore, the intensity and frequency of heatwaves can be reduced if the global community adopts and adheres to a lower emissions scenario in the future.