Water temperatures fluctuate in time and space, creating diverse thermal regimes on river networks. Temporal variability in these thermal
landscapes has important biological and ecological consequences because of nonlinearities in physiological reactions; spatial diversity in
thermal landscapes provides aquatic organisms with options to maximize growth and survival. However, human activities and climate change
threaten to alter the dynamics of riverine thermal regimes. New data and tools can identify particular facets of the thermal landscape that
describe ecological and management concerns and that are linked to human actions. The emerging complexity of thermal landscapes demands innovations in communication, opens the door to exciting research opportunities on the human impacts to and biological consequences of
thermal variability, suggests improvements in monitoring programs to better capture empirical patterns, provides a framework for suites of
actions to restore and protect the natural processes that drive thermal complexity, and indicates opportunities for better managing thermal
landscapes.