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Background and Aims Studies of the interactive effects of drought and high temperature on the physiological responses of grapevines (Vitis spp.) are scarce. We tested whether well-watered, potted vines were able to avoid heat waves through evaporative cooling in comparison to those suffering from water deficit. Methods and Results A greenhouse experiment was conducted with own-rooted Malbec grapevines under two water regimes, well-watered (100% of pot capacity) and water deficit (50% of pot capacity), and two air temperature regimes, high (45/22 degrees C) and Control temperature (35/20 degrees C). Short-term stomatal and non-stomatal regulation of photosynthesis was assessed by measuring leaf gas exchange, stomatal conductance (g(s)) and chlorophyll fluorescence. Whole-plant transpiration and vegetative growth were also measured. In well-watered vines, high air temperature increased g(s) and leaf transpiration (E-leaf), which decreased leaf temperature and increased vegetative growth, whole-vine transpiration and leaf net photosynthesis (P-n). Water deficit strongly reduced growth, P-n, g(s) and E-leaf. For vines under high temperature, however, reduction in P-n, g(s) and E-leaf was smaller than for that under the Control temperature. Conclusions Evaporative cooling may help well-watered grapevines withstand heat waves and avoid irreversible reduction in gas exchange and chlorophyll fluorescence. Significance of the Study This study improves our understanding of grapevine response to a heat stress and water deficit, which are both predicted to increase with climate change.