A “heat wave” occurs when summertime temperatures in North-Western India are abnormally high—above the average maximum temperature. Heat waves usually happen from March through June; in certain extreme circumstances, they may even last into July. People who live in these areas suffer greatly from the extreme temperatures and the resulting atmospheric conditions, which can sometimes be fatal due to physiological stress.

• Heat waves are not considered when a station’s maximum temperature reaches 40 degrees Fahrenheit for Plains regions and 30 degrees Fahrenheit for Hilly areas.
• Heat Wave Departure from normal is 5oC to 6oC when a station’s normal maximum temperature is less than or equal to 40 C.
• A heat wave departs from normal by 4 to 5 degrees Celsius, and a severe heat wave departs from normal by 6 degrees Celsius or more when a station’s normal maximum temperature is above 40 degrees Celsius.
• It is appropriate to declare heat waves regardless of the average maximum temperature, provided that the temperature stays at 45 degrees or above.”
•  Globally, longer, more intense heat waves and daily peak temperatures are becoming more common due to climate change.
•  India is experiencing increased health risks due to more frequent and intense heat waves, leading to increased deaths.

Due to climate change, longer, more intense heat waves and higher daily peak temperatures are becoming more common globally. India is experiencing increased health risks due to more frequent and intense heat waves, leading to increased deaths.

• Heat waves can cause dehydration, cramping, heat exhaustion, and heat stroke, among other health effects. The following are the indications and symptoms:
• Heat cramps: Fever below 39 C, or 102 F, is typically present along with oedema (swelling) and syncope (fainting).
• Fatigue, weakness, headache, nausea, vomiting, muscle cramping, and sweating are all signs of heat exhaustion.
• Heat Stoke: Delirium, convulsions, or coma, as well as body temperatures of 40 C, or 104 F, or higher. This illness has the potential to be fatal.

Heat Wave and Health

The timing, severity, and length of a temperature event, the degree of acclimatisation, and the degree to which the local population, institutions, and infrastructure can adjust to the current climate all influence the extent and type of health effects associated with heat. With certain public health initiatives, the detrimental effects of heat on health are predictable and mainly avoidable. All humans are susceptible to a wide range of physiological effects from prolonged exposure to heat, many of which worsen pre-existing conditions and cause premature death and disability.  

Some key health impacts of heat are:

• Exposure to hotter temperatures can lead to sudden heat gain, which compromises the body’s temperature regulation and results in ailments like heat exhaustion, heatstroke, cramps, and hyperthermia.
• Heat-related deaths and hospital admissions can happen very quickly (on the same day) or slowly (over several days), which can hasten death or illness in the already fragile. This is especially noticeable in the early stages of heat waves.  
• Extreme temperature variations can exacerbate long-term health issues, such as diabetes-related disorders and diseases of the heart, lungs, and brain.
• Important indirect health effects of heat are also present. Heat can affect how people behave, how diseases spread, how well health services are provided, and how clean the air is.