Ganga river basin is the lifeline of the most of the North Indian population. Upper Ganga river basin is the source of Ganga river where Ganga river originates form Gangotri glacier. Many articles, researches are claiming that most of the Himalayan glaciers are receding due to rising temperature caused by climate change. In this study it is tried to find the changes in average temperature in the month of December. High resolution gridded monthly temperature data provided by Climate Research Unit (CRU) for 116 years, i.e., from year 1901 to 2016 is used. Least square linear trend shows upward trend in most of the regions. Significance of these trends is checked using non-parametric Mann-Kendal (MK test) at 5% significance level and found significance for most of the Southern regions of basin. Assessment of time of change detection is one of the important tasks for any climate change study. Here, time of change is found out using Non-parametric Cumulative -Deviation test at 5% significance level. It is found that most of the regions of Gangetic plains show change in the year 1988. No change in detected in the upper reaches of Ganga river. So, the plains of Upper Ganga river basin are found to be highly affected by climate change and winter temperature is rising significantly.