Precipitation is a relevant climatic variable for building and urban design in hot climates, because of its potential to naturally mitigate heat excess in buildings and cities by evaporative cooling; and as a primary source of water to artificially reproduce this cooling mechanism, particularly in the humid tropics and subtropics. However, precipitation is commonly neglected in the analysis and development of climate responsive architecture and is rather seen as a cause of problems. This paper proposes a practical graphical method for building designers and planners which facilitates the meaningful 'reading' of a climate, to reveal the potential use of precipitation in architecture. This method supplements existing climate analysis tools by defining a scale and benchmarks that easily link potential water requirements of buildings with water availability from precipitation. To complement this method, the concept of Urban Precipitation Surplus is also proposed, a measure of the excess of precipitation that is usually discarded which could be exploited for building cooling and contribute to regenerate the water cycle and improve microclimates in cities. Finally, a brief discussion is given about the analogy between buildings and vegetation, and the importance of enriching architecture with concepts from fields like agriculture and climatology.