This paper examines the conceptions of planetary phenomena related to temperature change as held by primary school teacher trainees at the Department of Teacher Education of Jyväskylä University. The data were collected by means of an essay test, supplemented by interviews. The results show that very few students have internalized these phenomena in accordance with present‐day scientific concepts. The significance of the Earth's sphericity seems particularly obscure. The influence of the angle of inclination of the Earth's axis is misunderstood. Similarly, temperature differences are erroneously attributed to the distance from the sun of the Earth or of a particular place. The students do not reach their conclusions by inference, but rather attempt to remember what they have been taught. There are defects in their logical thought, several answers contained no explanation whatsoever, and cause‐and‐effect relationships are reversed.