Heatwave days to double in Chennai, Avadi, Tambaram; 21 cities in Tamil Nadu to feel the fire

CHENNAI: If the heatwave was unbearable this year, buckle up as the number of heatwave days will double before 2050 (26 years) in 21 cities in the state, including Chennai, Tambaram and Avadi.

What makes the situation worse is that Chennai has a green space deficit of 62 sq km.

According to a draft report titled ‘Climate Risk Assessment and Adaptation Plan of Tamil Nadu – Sustainable Habitat’ prepared by the Center for Climate Change and Disaster Management (CCCDM) at Anna University (1990-2020), conditions of thermal discomfort are escalating , especially in northern coastal areas, have had a significant impact on urban areas.

Projections indicate a worrying trend of increasing thermal discomfort, which could reach 250 days per year in the near century (2050). “City Climate Risk Assessment highlights that the cities in the northern coastal areas such as Greater Chennai Corporation and the surrounding areas of Avadi, Tambaram are exposed to high levels of climate hazards. Tirunelveli, Tiruchy, Thanjavur, Kumbakonam, Madurai, Sivakasi, Dindigul, Nagercoil, Kancheepuram, Thoothukudi, Cuddalore and Salem are at moderate risk of climate change, while Karur, Tiruppur, Hosur, Coimbatore, Erode and Vellore are at low risk,” it said report. .

Stating that the intensified urban heat island effect and extreme temperatures are endangering urban areas, the study states that Chennai, Nagercoil, Thanjavur and Thoothukudi experienced an average of more than 40 heatwave days per year between 1985 and 2014. The number of heat wave days is expected to double in the next century.

If the maximum temperature is more than 4.5 degrees Celsius than the normal temperature, the Indian Meteorological Department calls it a heat wave.

The annual average heat wave days in Chennai will increase to 81 days from the current 42 days. Similarly, the annual average heatwave days in Avadi and Tambaram will increase from 43 and 42 days to 80 and 78 days, respectively. Kancheepuram, which has 39 heatwave days, will have 74 heatwave days by 2050, according to the study.

Of all the 21 cities, which will experience a higher number of heat wave days in the future, Chennai would be the worst affected. “The overall exposure assessment shows that Chennai, with the highest population density and a large number of homeless people, is the most exposed city in Tamil Nadu. Poor infrastructure and socio-economic factors make these groups more vulnerable to heat stress and related diseases,” the report said.

Attributing the higher number of heat wave days to lack of green cover, the study states that Chennai has a green space deficit of 62 sq km, which is the highest among the 21 cities, as per the Urban Greening Guidelines, 2014.

Out of about 438 sq km of its total area, Chennai has only 8 sq km of green cover, exceeding the recommended requirement of 79 sq km. In addition, 9 square kilometers have potential for additional green cover.

Coimbatore has only 7 sq km of green cover as against the recommended 60 sq km. The city has an additional potential of 13 square kilometers, but a deficit of 40 square kilometers. On the other hand, Avadi has a deficit of 5 square kilometers.

Interestingly, Kancheepuram and Tambaram along with Nagercoil have no shortage. Under the guidelines for urban greening, the Ministry of Urban Development recommends that the share of recreational areas, including parks, open spaces, water bodies and others, in the total developed area in medium and large cities should be between 18 and 20%. In metropolitan cities, this share should be 20-25%.

“In this situation, it is crucial to improve green coverage in cities with the lowest green spaces per capita. The cities with more than the recommended green cover should be preserved without further degradation due to the ever-growing population in the future. Although urban forestry is man-made, the results indicated that more attention should be paid to the management of urban forestry,” the report advises.

On the other hand, increasing temperature and heat wave would affect plant growth and biodiversity due to the reduction in isothermality (the extent to which temperature varies throughout the year). The isothermality ranged from 51 to 67 in the cities of Tamil Nadu during 1985-2014, decreasing to 48-65 in the near century.

A reduction in isothermality will lead to higher daytime temperatures in cities. “High temperatures worsen air pollution. Chemical reactions in the atmosphere increase the formation of ground-level smog and ozone,” the report said.

The State Environment, Forest and Climate Change Department is in the process of formulating an urban green policy to increase green cover in the cities. “The policy for all of Tamil Nadu will cover various aspects of greening the city by creating urban parks, planting avenues, vertical gardens and green belts around the industrial areas,” a senior environment department official said .

The official added that urban greening policies will be part of the Green Tamil Nadu Mission. For the implementation, there will be a special wing in cities and companies, consisting of botanists, horticulturists, landscape architects and others.

Required green space (in square kilometers)


Existing green cover



8 71


7 53


4 22


17 38


2 9


1 7


2 2

Annual average heat wave days


Basic period Almost century


Near century



42 81


43 80


42 78


39 74


44 67


32 54


29 50