A review of field and laboratory investigations suggests that many ectothermic vertebrates can exploit the spatiotemporal distribution of environmental temperatures to maximize energy utilization and to enhance survivability. Diel and seasonal cycles in thermal preference, acclimation rate, thermal tolerance and heat-hardening may well be adapted to temporal variations in environmental temperature. In addition, many ectoiherms behaviorally exploit thermal heterogeneity in the environment. Such behavioral adaptations are synergistic with various degrees of physiological regulation. Voluntary brief exposures to temperatures that would be lethal upon prolonged exposure can result in heat-hardening. Heat-hardening, distinct from acclimation to high temperature, is a short-term increase in thermal tolerance while tolerance acclimation is a longer lasting response within normal ranges of environmental temperatures; both are reversible nongenetic responses. The physiological and ecological significance of behaviorally mediated heat-hardening may be greater than previously realized and suggest new approaches for future study.