The automotive industry is currently facing major changes of its development due to new social, environmental and economic challenges. The sector needs to find sustainable solutions which do not hinder the customers' expectancies. The solutions extend from combustion engine optimization up to vehicle electrification. Drivetrain electrification is currently a topic of high interest and in the case of hybrid vehicles, the design focus is set on the power density and the efficiency. Beside the electric machine technologies, the cooling system plays a preponderant to meet the requirements of the sector especially concerning the continuous power and the repeatability of the performance. Due to the complexity of developing multiphase cooling system, it is necessary to consider the topic during the early development phase to achieve the maturity required for the implementation in a vehicle. The increasing electrification of the vehicles sets higher challenges for the electrical as well as the thermal design of the machine. Hence reliable and accurate modelling approaches are required. This paper is focused on the thermal modelling of electric machine considering the automotive boundary conditions. The paper describes therefore the required models for temperature estimation before discussing the influence of the machine environment on its performances."