Falling water droplets quickly assume surface temperatures equal to the wet‐bulb temperature of the air. Formulas for absolute humidity and Ferrel's psychrometric formula are used to develop a simple relationship for calculating the capacity of air to absorb water droplets evaporated into it. Such data are relevant for determining water losses during sprinkler irrigation, the discrepancy between radar observed liquid water contents and ground observed rainfall and other factors important in the hydrologic balance of the atmosphere. The evaporative capacity E₀ in g/m³ of the air is determined to be explicitly defined by an equation involving wet‐bulb temperature T_w in °K, wet‐bulb depression Δt_w in °C, and atmospheric pressure ρ in mb E₀ = (p·Δt_w)/(7T_w)