Climate change is one of the greatest challenges of our era, and identifying the most vulnerable populations is urgently needed to guide conservation efforts. Although over 40% of amphibian species are currently listed as threatened, our understanding of their resilience to rising temperatures remains limited. This is primarily because knowledge of thermal tolerance is taxonomically and geographically biased. Data on amphibian heat tolerance limits only covers 7.5% of known species and is geographically biased towards temperate regions. This discrepancy is problematic, considering the high species richness in the tropics and the mounting evidence that tropical ectotherms are most susceptible to rising temperatures. In this study, we aimed to resolve existing biases in physiological data to assess the vulnerability of amphibians to global warming at truly global scales. We first employed a novel data imputation approach to predict the heat tolerance of 60% of amphibian species with high accuracy. We then assessed their vulnerability to daily temperature variation in different thermal refugia (terrestrial, aquatic, arboreal) using biophysical models. We found that 198 out of 5203 species are already exposed to overheating events in shaded terrestrial conditions. Despite accounting for heat tolerance plasticity, a 4°C global temperature increase would create a step-change in impact severity, pushing 9.4% of species beyond their physiological limits. In the Southern Hemisphere, tropical species encounter disproportionally more overheating events, while in the Northern Hemisphere, non-tropical species are more susceptible. Our findings challenge common evidence for latitudinal gradients in overheating risk and underscore the importance of considering climatic variability in vulnerability assessments. Importantly, our predictions lead to clear directives for research and management - pointing to specific populations and species with increased risk, predominantly in under-studied regions of the Global South. Our microclimate-explicit analyses also demonstrate the crucial role vegetation and water bodies play in mitigating the impacts of heat waves on amphibians. Immediate action is needed to preserve and manage these vital microhabitat features.