The spinning rotor gauge (SRG) is a vacuum meter for the range 10@super -4@ Pa -to- 1Pa with good long term stability; therefore it is widely used as reference standard in calibration services. The calibration constant of the SRG is the effective accommodation coefficient @sigma@ valued around 1. This accommodation coefficient of the gas particles to the rotor is considered temperature independent for the normal operational temperatures 18°C -to- 30°C. We have carried out investigations that show that @sigma@ of an unbaked rotor (which is not unusual in calibration services) is temperature dependent. The operational temperature of the SRG could be varied from 16°C -to- 40°C. Typical relative changes of @sigma@ were 0.1% per 3 degree change of temperature, but larger changes were also observed. It will be discussed, if the changes are related to a change of H@sub 2@O coverage of the rotor.