We have recently proposed a semi-physical model of forest fire, validated for litters of pine needles at the laboratory scale under both wind and slope condition. With the aim to provide an operational management tool for the battles against forest fires, this model was simplified as well as the method for the identification of its parameters. This was necessary to obtain a computational time lower than the real time. The temperature being the state variable in our approach, its knowledge is essential and let to identify the model’s parameters. At the laboratory scale, this variable was measured by using thermocouples. However, these measurements are difficult to carry out at the field scale and the model must now be tested at this scale. To circumvent this difficulty, we have developed a method to measure the temperature in flames and embers, based on remote infra-red imaging. The paper is organized as follow. The method developed to measure the temperature in flame by using an infra-red camera is detailed in the second section. This relation is tested in the third section for several types of flames and compared with a classical method. The proposed method in used in the fourth section to identify the parameters of the model of forest fire.