Water sorption isotherms describe an equilibrium relation between the water content in a product and the relative humidity of surrounding air. The course of sorption isotherms of products, even of such simple products as sugar, depends on many factors. While determining the water vapour, those factors impact the storage stability of products. The objective of the paper was to determine the effect of temperature on the course of sorption isotherms of sugar. Samples of commercial, beet white sugar constituted the research material. Sorption curves were determined at a temperature of 5, 10, and 25°C using a method developed on the basis of data taken from the expert literature. It was found that under the same relative humidity of air, the decreased storage temperature caused an essential increase in water content in the samples studied.