About Heat Wave

Heat-wave is defined as,

“The condition where maximum temperature at a grid point is 3˚C or more than the normal temperature, consecutively for 3 days or more.”

World Meteorological Organization defines a heat wave as five or more consecutive days during which the daily maximum temperature exceeds the average maximum temperature by five degrees Celsius”.

Heat-wave early warnings are designed to reduce the avoidable human health consequences from heat-waves through timely notification of prevention measures to vulnerable populations. Heat wave is considered only after maximum temperature of a station reaches at least 40o C for plains and at least 30o C for hilly regions. India Meteorological Department issues forecasting on the level of Heat waves likely to prevail in the regions for 5 days at a time.

The State of Tamil Nadu, which is located in the vulnerable part of the Indian Peninsula, is subject to climate and geological related disasters viz., cyclone, flood, earthquakes, tsunami and drought to varying degrees. In the recent years, due to rising temperatures during the summer/ pre-monsoon months several places are subject to ‘Heat wave’ conditions.

India Meteorological Department (IMD) criteria for Heat Wave and Severe Heat Wave:

Heat wave is considered only after maximum temperature of a station reaches at least 40° C or more for plains, at least 30° C or more for hilly regions and 37° C or more in sea shore areas

Early Warning and Indicators of heat-wave

In response to the devastating mortality and  morbidity  of  recent  heat-wave  events,  many  countries  have  introduced  heat-wave  early warning systems. Heat-wave early warnings are designed to reduce the avoidable human health consequences from heat-waves through timely notification of prevention measures to vulnerable populations.  India Meteorological Department has developed criteria for heat waves based on the temperature at stations and is issuing weather warning forecasting on the level of Heat waves likely to prevail in the regions for 5 days at a time. The Regional Meteorological Centre (RMC) in Chennai has been publishing weather projections for Tamil Nadu on its website, keeping people informed with regular updates of projections of average temperatures for a week ahead for every district in the state. Such information can   provide timely warning to the public to take adequate precautions to prevent being affected by the heat wave and thus mitigate the disaster.

High Risk Groups

  • Children, Pregnant women & Senior citizens
  • Labourers including those at construction sites/Outdoor workers/Farmers/MNREGS workers
  • Police personnel/security staff
  • Industrial workers working at High Temparatures
  • Street hawkers/Salesmen
  • Riksha pullers/auto drivers/Travellers/bus drivers
  • Coolies/Slum residents/Beggars/Homeless
  • Chronic sick/indoor cases
  • Patients on drug treatment
  • Addicts (Alcohol, drugs etc)

Preparedness measures:

  • Ensure drinking water supply to all habitations.
  • Local bodies shall identify the areas to provide shelters and drinking water during heat alert period such as bus depots/stops, markets, railway stations, pilgrimage, tourist, industrial areas etc.
  • District Administration have to prioritize maintaining power to critical facilities such as hospitals and UHCs.
  • Checking of inventories of medical supplies including IV fluids, cooling packs or ice, ORS powder in PHCs, UHCs, and 108 emergency ambulances.
  • Adequate arrangements for treatment of heat stroke patients round the clock.
  • Display of prevention measures to overcome HEAT WAVES.
  • Ensure the services of 108 / 104 Emergency Service with adequate supply of IV fluids.
  • Establish mobile Health teams to cover major bus stands / Terminals, pilgrimage, tourist centres and other public places.
  • Keep open the parks in afternoon and for a longer duration during evenings.
  • Labour department to enforce better working conditions for workers such as provision of sheds, safe drinking water, bathing facilities etc as per the Labour Act.
  • Fire and Rescue Services Department has to ensure the readiness of vehicles and fire fighting equipment to face any emergency.
  • Police personnel on duty in the open, to be educated on precautionary measures to be taken during heatwave.
  • Shelters for traffic police may be provided, wherever feasible.
  • Children in anganwadis and schools may be advised to ensure that they are not exposed in the sun.
  • To collect information on the works sanctioned under MGNREGS programme in High risk areas to plan for mitigation effort during heat period.
  • MGNREGS workers shall be educated in following the do’s and don’ts. Adequate water, shelter should be provided as per the rules prescribed under MGNREGS. It is to be ensured that the children of MGNREGS workers are also adequately taken care of and not exposed to sun.

Veterinary Measures:

Animal care

  • Poultry and cattle will also be adversely affected during heat wave. Cattle and poultry owners to be cautioned accordingly.
  • Ensure adequate stock of medicines in all veterinary hospitals for treatment of cattle /poultry birds.
  • Ensure provision of water in veterinary dispensaries

Wild life

  • Provision of water supply to animals in reserved/protected areas and in zoos.

Public Awareness and community outreach measures:

  • Release of messages on DOs / Don’ts to the general public and vulnerable groups about Heat wave.
  • Utilize local radio, FM broadcasts, cinema theatres, print and social media to disseminate heat protection tips and high temperature warnings to the vulnerable sections.
  • Preparation of Posters & pamphlets with tips to take care of cattle and poultry during heat waves.
  • Local bodies to take a lead role in creating awareness.
  • Public should be cautioned not to venture into the forests without permits, since forests are prone to fires during summer

Capacity Building/ Training programmes:

  • Medical & Health Department officials shall be advised to conduct training programs/orientation course on heat illness for medical staff.
  • Training of school teachers to equip them with knowledge of heat protection tips and activities which they can disseminate in classrooms.

Involvement of Governmental and Non-Governmental Organisations:

Actively involve NGOs / Rotary Clubs / Lions Clubs and Corporate houses as part of Corporate Social Responsibility to provide shelters, drinking water (Thaneer pandal) during heat days.


  • Listen to Radio, watch TV, read Newspaper for local weather forecast to know if a heat wave is on the way.
  • Drink sufficient water and as often as possible, even if not thirsty.
  • Wear light weight, light-coloured, loose, and porous cotton clothes. Use protective goggles, umbrella/hat, shoes or chappals while going out in sun.
  • While travelling, carry water with you.
  • If you work outside, use a hat or an umbrella and also use a damp cloth on your head, neck, face and limbs.
  • Use ORS, coconut water homemade drinks like lassi, torani (rice water), lemon water, buttermilk, etc. which help to re-hydrate the body.
  • Recognize the signs of heat stroke, heat rash or heat cramps such as weakness, dizziness, headache, nausea, sweating and seizures. If you feel faint or ill, see a doctor immediately.
  • Urine in darker yellow or orangish yellow indicates severe dehydration.
  • Keep animals in shade and give them plenty of water to drink.
  • Keep your home cool, use curtains, shutters or sunshade and open windows at night.
  • Use fans, damp clothing and take bath in cold water frequently.
  • Provide cool drinking water near work place.
  • Caution workers to avoid direct sunlight.
  • Schedule strenuous jobs to cooler times of the day.
  • Increasing the frequency and length of rest breaks for outdoor activities.
  • Pregnant workers and workers with a medical condition should be given additional attention.


  • Do not leave children or pets in parked vehicles.
  • Avoid going out in the sun, especially between 12.00 noon and 3.00 p.m.
  • Avoid wearing dark, heavy or tight clothing.
  • Avoid strenuous activities when the outside temperature is high. Avoid working outside between 12 noon and 3 p.m.
  • Avoid cooking during peak hours. Open doors and windows to ventilate cooking area adequately.
  • Avoid alcohol, tea, coffee and carbonated soft drinks, which dehydrates the body.
  • Avoid high-protein food and do not eat stale food.


If Heat Stroke is suspected, call 108 immediately. While waiting for the ambulance:

  • Make the victim like down
  • Take the person’s temperature.
  • If possible move the affected person to somewhere cooler / shaded area.
  • Apply cold compresses
  • Elevate feet
  • Give a cool shower by sprinkling with water or Wrapping in a damp sheet and using a fan to create an air circulation.
  • Encourage to drink fluids, if they are conscious.
  • Do not give aspirin or paracetamol.