This paper deals with the estimation of the plate temperature in heavy plate rolling. An Extended Kalman Filter (EKF) is designed and its initialization and parametrization are discussed in detail. The observer is validated by means of experimental data recorded during a measurement campaign with a special developed test plate instrumented with thermocouples. It is shown that a good estimation accuracy can be achieved under normal production conditions despite the scarcity of measurements. Furthermore, the coupling effect between the plate and the work rolls is investigated in more detail. Based on this analysis, the validity of a computationally inexpensive reduced observer is demonstrated. (C) 2014 Elsevier Ltd. All rights reserved.