In temperatures exceeding 40°C, staying cool is crucial for survival, especially in India, where buttermilk (chaas) and lassi are popular beverages. The primary distinction lies in their composition: buttermilk is diluted with water, making it lighter and more hydrating, while lassi is thicker and often includes sugar or cream, which can slow digestion. This slower processing can leave one feeling sluggish in extreme heat. Buttermilk's electrolyte-rich, low-fat profile aids in quick hydration and temperature regulation, making it ideal for hot weather. Conversely, lassi provides nourishment and probiotics but is better consumed in moderation during heatwaves. Ultimately, for rapid cooling and hydration, buttermilk is the superior choice, while lassi serves as a satisfying, albeit heavier, option.