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Heat Wave

What is a heat wave

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 parts of India. Heat Waves typically occur between March and June, and in some rare cases even extend till July. The extreme temperatures and resultant atmospheric conditions adversely affect people living in these regions as they cause physiological stress, sometimes resulting in death.

Criteria for Heat Wave

IMD has given the following criteria for Heat Waves:

  • Heat Wave need not be considered till maximum temperature of a station reaches atleast 40oC for Plains and atleast 30oC for Hilly regions
  • When normal maximum temperature of a station is less than or equal to 40oC Heat Wave Departure from normal is 5oC to 6oC Severe Heat Wave Departure from normal is 70C or more
  • When normal maximum temperature of a station is more than 40oC Heat Wave Departure from normal is 4oC to 5oC Severe Heat Wave Departure from normal is 6oC or more
  • When actual maximum temperature remains 45oC or more irrespective of normal maximum temperature, heat waves should be declared. Higher daily peak temperatures and longer, more intense heat waves are becomingly increasingly frequent globally due to climate change. India too is feeling the impact of climate change in terms of increased instances of heat waves which are more intense in nature with each passing year, and have a devastating impact on human health thereby increasing the number of heat wave casualties.
  • Higher daily peak temperatures and longer, more intense heat waves are becomingly increasingly frequent globally due to climate change. India too is feeling the impact of climate change in terms of increased instances of heat waves which are more intense in nature with each passing year, and have a devastating impact on human health thereby increasing the number of heat wave casualties.

Health Impacts of Heat Waves

  • The health impacts of Heat Waves typically involve dehydration, heat cramps, heat exhaustion and/or heat stroke. The signs and symptoms are as follows:
  • Heat Cramps: Ederna (swelling) and Syncope (Fainting) generally accompanied by fever below 39oC ie 102oF.
  • Heat Exhaustion: Fatigue, weakness, dizziness, headache, nausea, vomiting, muscle cramps and sweating.
  • Heat Stoke: Body temperatures of 40oC ie 104oF or more along with delirium, seizures or coma. This is a potential fatal condition

Do's and Dont's

What to do during a Heat Wave

  • Listen to Radio; watch TV; read Newspaper for local weather news or download weather information related mobile app.
  • Drink sufficient water - even if not thirsty. Persons with epilepsy or heart, kidney or liver disease who are on fluid-restricted diets; or have a problem with fluid retention should consult a doctor before increasing liquid intake.
  • Use ORS (Oral Rehydration Solution), homemade drinks like lassi, torani (rice water), lemon water, buttermilk, coconut water, etc. to keep yourself hydrated.
  • Traditional remedies like onion salad and raw mango with salt and cumin can prevent heat stroke.
  • Wear lightweight, light-coloured, loose, cotton clothes.
  • Stay indoors as much as possible.
  • If outside, cover your head: Use a cloth, hat or umbrella. Use sunglasses to protect your eyes and sunscreen to protect your skin.
  • Recognise the signs of heat stroke, heat rash or heat cramps such as weakness, dizziness, headache, nausea, sweating and seizures.
  • If you feel dizzy or ill, see a doctor immediately or ask somebody to take you to the doctor immediately.
  • Rest in shade, take breaks if you must work in the sun
  • Place a cool, wet cloth on your head to cool off
  • Take special care for the elderly, children, sick or overweight as they are more likely to become victims of excessive heat.
  • Offer water to vendors and delivery people who come to your home or office.
  • Grow more trees
  • Use public transport and car-pooling. This will help reduce global warming and heat
  • Conserve water bodies. Practice rainwater harvesting.
  • Use energy-efficient appliances, clean fuel and alternative sources of energy.

Employers and Workers

  • Provide cool drinking water at the workplace.
  • Provide resting shade clean water, buttermilk, first-aid kits with ice-packs and ORS (Oral Rehydration Solution) for all workers.
  • 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.
  • Give lighter work and shorter hours to workers new to a high heat area.
  • Pregnant women and workers with a medical condition should be given additional attention.
  • Notify workers about heat wave alerts

What not to do during a Heat Wave

  • Do not go out in the direct sun, especially between 12.00 noon and 3.00 p.m.
  • Avoid extensive physical activity, when outside in the afternoon.
  • Do not send children or pets out in the sun or leave them in closed vehicles.
  • Avoid alcohol, tea, coffee and carbonated soft drinks, which dehydrates the body.
  • Avoid high-protein, salty, spicy and oily food. Do not eat stale food.
  • Avoid wearing dark, heavy or tight clothing
  • Avoid cooking during peak heat hours. If you must cook, open doors and windows to ventilate the cooking area adequately.
  • Don’t burn dry leaves, agriculture residue and garbage.
  • Do not go out barefoot.
  • Avoid cooking during peak hours. Open doors and windows to ventilate cooking area adequately.
  • Avoid using incandescent light bulbs which may generate unnecessary heat, as can computers or appliances.Tips to treat a person affected by heat wavceRecover and Build

Tips to treat a person affected by Sun stroke

If you think someone is suffering from the heat:

  • Move the person to a cool place under the shade
  • Give water or ORS to drink or lemon sarbat / torani or whatever is useful to rehydrate the body.
  • Fan the person
  • Consult a doctor if symptoms get worse or are long lasting or the person is unconscious
  • Do not give alcohol, caffeine or aerated drink
  • Cool the person by putting a cool wet cloth on his/her face/body
  • Loosen clothes for better ventilation
  • If consistently experiencing high body temperature, throbbing headache, dizziness, weakness, nausea or disorientation in the summer, call an

For a cooler home

  • Use solar reflective white paint, cool roof technology, air-light and cross ventilation and thermocol insulation for low-cost cooling. You can also keep haystacks or grow vegetation on roofs.
  • Install temporary window reflectors such as aluminium foil-covered cardboard to reflect heat back outside. 
  • Keep your home cool, use dark colour curtains, tinted glass/ shutters or sunshade and open windows at night. Try to remain on the lower floors.
  • Green roofs, green walls and indoor plants reduce heat by cooling the building naturally, reducing air-conditioning requirements and release of waste  heat.
  • Maintain AC temperature at 24 degrees or higher. This will reduce your electricity bill and make your health better.
  • While constructing a new home
    • Use cavity wall technology instead of regular walls.
    • Construct thick walls. They keep the interiors cool.
    • Construct lattice walls and louvered openings. They allow maximum air flow while blocking the heat.
    • Use natural materials like lime or mud to coat walls.
    • Avoid glass, if possible.
    • Consult a Building Technology expert before construction.

Protect Cattle from heat waves

  • Keep animals in shade and give them plenty of clean and cold water to drink.
  • Do not make them work between 11am to 4pm.
  • Cover the shed roof with straw, paint it white or plaster with dung-mud to reduce temperature.
  • Use fans, water spray and foggers in the shed.
  • During extreme heat, spray water and take cattle to a water body to cool off.
  • Give them green grass, protein-fat bypass supplement, mineral mixture and salt.
  • Make them graze during cooler hours.

Emergency Kit

  • Water bottle
  • Umbrella/ Hat or Cap / Head Cover
  • Hand Towel
  • Hand Fan
  • Electrolyte / Glucose / Oral Rehydration

Source: National Disaster Management Authority(NDMA),Government of India

Last Modified : 11/16/2023

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