Variable Sensitivity of Lake Surface Temperatures to Short‐ and Long‐Term Atmospheric Warming

Plain Language Summary: Lakes respond differently to gradual, long‐term atmospheric warming and short, intense heatwaves. Using satellite and modeled data from over 35,000 lakes, we found that lake surface temperatures track about 76% of long‐term air temperature (AT) increases—meaning that for every 1°C rise in AT, water temperature increases by roughly 0.76°C. During heatwaves, lakes respond most strongly to their duration, with an average sensitivity of 84%, while sensitivity to heatwave frequency or intensity is lower (55%–59%). Interestingly, sensitivity to long‐term atmospheric warming is negatively correlated with sensitivity to atmospheric heatwaves: lakes that warm rapidly under gradual warming do not necessarily respond as strongly to short‐term extremes. These patterns are shaped by sunlight, wind, evaporation, and lake location. More incoming solar radiation increases sensitivity to heatwaves, while stronger winds reduce sensitivity by mixing the water and dissipating heat. Overall, lake warming is complex and nonlinear. Lakes respond in different ways to gradual atmospheric warming and short‐term heat extremes, which can affect stratification, oxygen levels, and the growth of algae. Understanding these responses is critical for predicting how climate change will influence water quality, aquatic ecosystems, and the availability of freshwater resources in the future.