This Demonstration shows how the rate of evaporation of water from a flat surface changes with temperature, wind speed, drying time, solar irradiance, air pressure and relative humidity. Selecting a location determines the last three variables, while the first three are controlled with sliders. The changing level of water in the beaker serves as a proxy for the amount of water that would evaporate from a hanging shirt under such conditions. The moving water molecules on the T-shirt serve as a visual representation of the process of evaporation as they turn into water vapor above the shirt and eventually dissipate into the atmosphere.