Abstract: The amount of rainfall received over an area is an important factor in assessing availability of water to meet various demands for agriculture, industry, irrigation, generation of hydroelectricity and other human activities. Over the study period of recent 30 years, trend values of monsoon average rainfall in Sylhet have decreased. This paper has measured the correlation coefficients between rainfall and time for Sylhet, where correlation coefficient for Sylhet is negative. In order to check the strength of linear relationship between rainfall and time, P-value has been measured. Due to various factors of Sylhet region of Bangladesh, there is a growing need to study the rainfall pattern, and also frequency of the heavy rainfall events. This study was checked annual average rainfall of 30 years for this region. It is hoped that this research may be of help to the concerned organizations and experts working on increasing rainfall problem in Chittagong.