Recent advances in quantifying biochemical and cellular-levelresponses to thermal stress have facilitated a new explorationof the role of climate and climate change in driving intertidalcommunity and population ecology. To fruitfully connect thesedisciplines, we first need to understand what the body temperaturesof intertidal organisms are under field conditions, and howthey change in space and time. Newly available data logger technologymakes such an exploration possible, but several potential pitfallsmust be avoided. Body temperature during aerial exposure isdriven by multiple, interacting climatic factors, and extremesduring low tide far exceed those during submersion. Moreover,because of effects of body size and morphology, two organismsexposed to identical climatic conditions can display very differentbody temperatures, which can also be substantially differentfrom the temperature of the surrounding air. These same factorsdrive the temperature recorded by data loggers, and one loggertype is unlikely to serve as an effective proxy for all organismsat a site. Here I describe the difficulties involved in quantifyingpatterns of body temperature in intertidal organisms, and explorethe implications of this complexity for intertidal physiologicalecology. I do so using data from temperature loggers designedto mimic the thermal characteristics of the mussel Mytilus californianus,and deployed at multiple sites along the West Coast of the UnitedStates. Results indicate a highly intricate pattern of thermalstress, where the interaction of climate with the dynamics ofthe tidal cycle determines the timing and magnitude of temperatureextremes, creating a unique "thermal signal" at each site.