Vernacular architecture is still very popular and constructed widely in North-East India. In this paper, the result of long-term monitoring of two vernacular houses selected one in Tezpur (warm and humid climate) and other one in Cherrapunjee (cold and cloudy climate) are presented. Long-term monitoring work includes the measurements of temperature (inside and outside house), relative humidity (inside and outside house) and illumination level (inside and outside house) for 25 days in all the seasons (January: winter, April: spring/pre-summer.july: summer/monsoon and October: autumn/pre-winter) of the year 2008. Temperatures profile across all the seasons represents strong daily and seasonal fluctuations. Formulae have been developed based on part of the monitoring data to predict the indoor maximum, average and minimum temperatures inside the same house occupied by the same family. The predicted formulae were developed based on the measured data for the month of January and July and were validated with the measured data of April and October months. It is found that the correlation coefficient (R-2 value) is above 0.96 for all the six formulae for the entire monitoring period. (C) 2010 Elsevier B.V. All rights reserved.