The issue of climate change has emerged very strongly during the last two decades on global scale in view of its projected implications on the environment of vulnerable states. Steadily rising temperature and its impacts on the cryosphere, rainfall and river flows are evident in many regions around the world. Changes in rainfall directly affect hydrology, water resources, agriculture, ecosystems, healthcare and disaster management sectors. Seen in the context of Pakistan, a country with very large population, agriculture based economy and high vulnerability index to natural disasters, it was important to ascertain climate variability and determine trends of temperature, rainfall and river flows on spatial and temporal basis. The study was conducted across the country to assess variations in mean minimum and maximum temperatures and rainfall in different climate zones of Pakistan. For this purpose datasets comprising 30 years of weather parameters from 1976 to 2005 were acquired from 30 meteorological observatories from different parts of the country based on the Kööpen classification system. In order to study the impact of change in temperature and rainfall on river flows, discharge record for the past 25 years of six relevant rivers was examined. The results of temperature analysis have indicated that the climatic zone located in high mountains in north, northwest and west have not been affected much as compared to the plain and coastal areas where a positive trend has been recognized. An increase of about 0.11°C/decade in mean temperature including 0.1°C/decade in minimum temperature and 0.12°C/decade in maximum temperature has been determined for Pakistan as a whole. On the one hand rainfall data has revealed an overall decline of -1.18mm/decade but on the other hand river discharges have increased in Indus and Swat rivers. Use of statistical models for forecasting future trends indicate an overall increase in the mean minimum & maximum temperature of the country till 2030 while rainfall shows a declining trend. Although the average increase of 0.11°C/decade is less than the global mean, the potential implications are far reaching. It is concluded that climate change phenomenon may be given key consideration in planning, designing, and implementing developmental schemes, food security, and disaster risk management sectors to adapt and mitigate undesirable scenarios.