This paper presents an experimental study of heat and mass transfer and phase transformations in the suppression of flaming combustion and thermal decomposition of model ground, crown, and mixed forest fires due to local exposure to water. The experiments were carried out with typical combustible forest materials (mixture of leaves, needles, and twigs) and models of trunks and branches of trees. The conditions and characteristics of suppression of the flaming combustion and thermal decomposition of combustible forest materials were determined. It is shown that in the case of crown and mixed fires, local short-term (a few seconds) action of a liquid projectile does not suppress the thermal decomposition of the material (but can only lead to localization of flaming combustion). In the case of ground forest fires, this approach can be efficient with an appropriate choice of the water-irrigated area of the combustion zone and the rate and time of water spraying.