McGuire is a coauthor on an invited commentary in the journal Hydrological Processes titled “Towards a unified threshold-based hydrological theory: necessary components and recurring challenges.” The paper developed from a session at last year’s American Geophysical Union meeting where the lead author and coauthors were the conveners and select speakers from the session. The paper explores organizing principles, making the ‘right’ measurements to observe thresholds, and using thresholds in cross-site comparisons. Threshold behavior in hydrological variables seem ubiquitous yet they are often difficult to identify or attribute to specific processes. This paper raises some issues and challenges incorporating thresholds into advancing hydrological understanding.