In this paper we propose an original technique based on the finite element method to couple electromagnetic and thermal homogenisation of multiturn windings. The model accurately accounts for skin and proximity effects considering the temperature dependence of electrical resistivity. We validate the approach by modelling a reference electrical machine open slot with representative boundary conditions. The case study refers to a particular wire shape and winding periodic configuration but the method can be applied to any symmetrical wire shape. The homogenisation allows us to efficiently evaluate the hot- spot temperature within the slot. The solution provided by the homogenised model proves to be very accurate over a large range of frequencies, when compared to the results using a fine model where all the conductors are physically reproduced.