This article offers a technique for predicting the fatigue life of metals by monitoring its surface temperature. The method is based on the examination of the cooling characteristics of a specimen once its temperature becomes steady and actuation halted. It is shown that the cooling curve is unique for a specific material and geometry regardless of the operating conditions such as the loading type, amplitude, and frequency. Using this finding along with the concept of fracture fatigue entropy (FFE), a technique is introduced to readily predict fatigue life in-situ. Results of extensive sets of experiments for cyclically actuated fully-reversed bending and tension-compression (TC) types of loadings, at different frequencies, and for various specimens’ geometries are presented to test the validity of the technique.