Climate change has significantly increased the earth's average surface temperature and heat waves have been predicted to increase in frequency, intensity and duration. Extreme heat events have increased the susceptibility to heat-related illnesses, such as heat exhaustion, heat stroke or death. Heat health action plans have been designed to advertise cooling behaviours to mitigate physiological strain. Heat health action plans suggest avoiding alcohol consumption during extreme heat as it may increase dehydration and impair behavioural or physiological temperature regulation and thermal perception. Regardless of these messages, alcohol sales continue to remain high during the summer months year after year, and 1/5 of adults identify alcohol as a hydration strategy during extreme heat events. A recent scoping review investigating the effects of alcohol and heat has demonstrated that acute alcohol consumption does not negatively influence thermoregulation, hydration, or hormone markers of fluid balance in the heat compared to a control fluid (https://doi.org/10.1186/s12940-024-01113-y). Further, alcohol consumption may elicit sex- and age-specific alterations in physiological and perceptual responses, neither of which have been explored. Therefore, this study aims to comprehensively evaluate how alcohol consumption systematically alters physiological responses and perceptions during conditions similar to those experienced indoors during extreme heat events in younger and older adults.