This work has been written within the framework of the theme chemistry in preschool. The purpose of the study is to provide knowledge about preschool children's perceptions of temperature in water. The study is based on a phenomenographic perspective. The data was collected with eight qualitative semi-structured interviews in connection with an experiment in a repeated process. The selection groups consisted of eight preschool children at the age of four to five years old. The result shows that preschool children conception temperature as something they can experience through their senses. They conception temperature as something they can easily connect to everyday life phenomena. The preschool children perceive that there is an event at an abstract level in the water that they cannot experience with the vision, the event differs depending on the temperature. Some children's perceptions were developed when they did get to face the learning object several times. The description categories identified in the analysis are: "smelling", "feeling", "steam", "dots", "smoke", "movement", "everyday life phenomena", "atoms", "anthropomorphic language" "heavy water and fast atoms "and" independent reasoning ". The result of this study can be used as a contribution to the preschool's natural science activities. For a wider understanding of taking advantage of and following children's natural science thoughts and descriptions. For an influential natural science teaching in preschool.