The invention relates to a temperature distribution determining apparatus (21) for determining a temperature distribution within an object, to which energy is applied, by using an energy application element (2). A first temperature distribution is measured in a first region within a first temperature range and a model describing a model temperature distribution in the first region and in a second region depending on modifiable model parameters is provided. A second temperature distribution is estimated in the second region within a second temperature range, while the energy is applied to the object, by modifying the model parameters such that a deviation of the model temperature distribution from the first temperature distribution in the first region is minimized. This allows considering the temperature dependence of the model parameters within the second temperature range, while estimating the second temperature distribution, thereby improving the accuracy of the estimation of the second temperature distribution.
