Water temperature is an important variable in river hydrology determining the biotic and abiotic processes of freshwater ecosystems. While many factors influence river water temperature on different spatial and temporal scales, air temperature remains the key variable that controls river water temperature fluctuations through atmospheric-water coupled interactions. Rising air temperature not only increases the long-term climatic states of water temperature but also modulates its interannual and intraseasonal variability and the severity and frequency of extremes. This talk will discuss our ongoing efforts to monitor and model water temperatures in several different river sites across northern British Columbia. The discussion will provide vital information on utilizing innovative field techniques, leveraging existing monitoring data, and implementing a water temperature modeling framework to study thermal regime changes in several rivers assisting the migration and spawning of different fish species. The results will synthesize the riverine thermal changes that many watersheds have experienced in the recent past by evaluating long-term water temperature trends, interannual and intraseasonal variability, and water temperature extremes.