Precipitation is known to play a major role in driving streamflow, especially in tropical regions. However, its influence can vary in colder, arid, or semi-arid climates. To better understand how precipitation and temperature affect streamflow in the Gunnison River Basin, we compared historical trends in climate variables and streamflow across six sub-basins within the region. We used statistical tools that don’t rely on assumptions about data distribution to explore the relationships between temperature, precipitation, and streamflow. To forecast future changes, we applied four different time series modelling techniques to each sub-basin. Our analysis showed that average temperature had a stronger and more consistent relationship with streamflow than precipitation did. We also observed sudden changes in precipitation and temperature patterns over time. In contrast, streamflow showed only small, gradual shifts, though these shifts varied from one time period to another. Importantly, we were able to identify the most suitable modelling approach for predicting future values of streamflow, temperature, and precipitation in the Gunnison River Basin. These findings are important for future water resource planning, as they highlight how streamflow may respond to ongoing climate changes. Water management strategies in the region should take these results into account.