The climate change issue is part of the larger challenge of sustainable development and one of the most important global environmental challenges facing humanity which go far beyond its effect on the environment. In order to understand the climatic change happening in the different agro-climatic regions of Tamil Nadu and to develop strategies to mitigate climatic stress and to optimise productivity monthly, Maximum and Minimum Temperature and Relative Humidity Data during the period 1955-2005 were obtained from the Indian Meteorological Department, Pune. From the basic temperature data, mean maximum, mean minimum and Temperature Humidity Index was computed for each month for the seven agro-climatic regions of Tamil Nadu. Mean maximum temperature was observed at the month of May, and Cauvery Delta zone showed maximum temperature of 38.22 AE 1.33 C with significant difference of P < 0.01 between the regions. Mean minimum temperature was observed at the month of January, and hilly zone showed minimum temperature of 5.59 AE 1.31 C with a significant difference of P < 0.01 between the regions. The long-term mean and annual compounded growth rates of T max , T min and THI were worked out on the basis of the representative areas selected for the study. The annual growth rate of maximum and minimum temperatures showed different patterns for different agroclimatic zones in the study area. The T max showed an increase in all the agro-climatic zones except in north-western zone and southern zone. T min also showed a positive growth pattern in all agro-climatic zones except in north-western zone and southern zone. The annual growth rate of THI showed different patterns for different agro-climatic zones. Five agroclimatic zones, viz., north-eastern zone, western zone and hilly zones, Cauvery Delta zone and high rainfall zone, were showing a positive