To help researchers to evaluate uniform but not stationary (thus transient) thermal conditions, we describe, show the performances and provide a new simple tool, which can be used to predict the whole-body dynamic thermal sensation and thermal comfort. The tool comprises a thermo-physiological model able to predict the body core and mean skin temperatures under uniform and transient environmental conditions and a dynamic thermal perception model, which uses the simulated temperatures to predict thermal sensation and thermal comfort. The selected thermo-physiological model is an updated version of the classical Gagge’s two-node model. For predicting the thermal sensation vote, we use an updated version of Fiala’s Dynamic Thermal Sensation (DTS) model. Finally, for modelling the last step of thermal perception, i.e. thermal comfort, we derive a new dynamic version of the well-known Fanger’s Predicted Percentage of Dissatisfied (PPD) index. We show that our novel models have better performances than the original ones. Furthermore, their simplicity and low computational cost are important advantages over more complex and computationally expensive multi-segment and multi-node thermo-physiological models.