Ukkola, AnnaPitman, A. J.Donat, M.G.De Kauwe, Martin GAngelil, O.2023-06-072023-06-070094-8276http://hdl.handle.net/1885/293360Land‐atmosphere coupling can amplify heat extremes under declining soil moisture. Here we evaluate this coupling in 25 Coupled Model Intercomparison Project Phase 5 models using flux tower observations over Europe and North America. We compared heat extremes (2.5% of the hottest days of the year) and the evaporative fraction (EF; a measure of land surface dryness) on the day the heat extremes occurred. We found a negative relationship between the magnitude of heat extremes and EF in both models and observations in transitional regions, with the hottest temperatures occurring during the driest days, with a similar but less certain relationship in dry regions. Surprisingly, many models also showed an amplification of heat extremes by low EF in wet regions, a finding not supported by observations. Many models may therefore overamplify heat extremes over wet regions by overestimating the strength of land‐atmosphere coupling, with consequences for future projections of heat extremes.This work was supported by the ARC Centre of Excellence for Climate Extremes (CE170100023). We acknowledge the National Computational Infrastructure at the Australian National University and the Earth System Grid Federation for making the CMIP5 model outputs available. We also gratefully acknowledge the World Climate Research Programme’s Working Group on Coupled Modeling, which is responsible for CMIP, and thank theclimate modeling groups (listed in Table S1) for producing and making available their model output.application/pdfen-AU© 2018. American Geophysical Union.201810.1029/2018GL0791022022-03-27