A suitably carried out hydrothermal treatment has an essential meaning for the production of quality peeled veneer. The course of hydrothermal plasticisation of wood in the process of preparing the veneer timber, intended for the production of peeled veneer, was monitored. In the JAVOR Pivka Company, d.d. the timber temperature placed at different positions in steam pit during steaming was measured. So was the rate of timber cooling from after finishing hydrothermal treatment until the beginning of timber peeling. 2 different measurement systems, Testo (177 T4) and Omega logger (OM-DAQPRO-5300), for measuring the temperature of veneer timber were used. The measurement systems Testo and Omega were reliable; the results of measuring were as expected. It was established that the production of veneer timber is influenced by the starting temperature of raw material as well as by the position of timber in a steam pit. The temperature of the surrounding (4.1 °C per hour on average) has the biggest influence on the rate of timber cooling after the finished hydrothermal treatment.