The purpose of this paper is to quantitatively demonstrate the influence of the temperature of the injected fluid, the fluid dynamic viscosity (dependent upon temperature), and the gas content in macro-pores on the development of a hydraulic fracture, fluid/gas pressures, and velocities during a small-scale hydraulic fracturing process in rock specimens under two-dimensional (2D) conditions. A novel DEM/CFD-based thermal-hydro-mechanical technique of pressurized fracturing laminar viscous fluid flow of a changeable temperature containing liquid and gas was developed for non-saturated porous materials with very low porosity. Fluid heat transfer involved both cohesive granular particles and the fluid (diffusion and advection) (conduction). DEM was employed to represent the mechanical behavior of the rock mass by using discrete spherical elements interacting through elastic-brittle normal connections that could break to generate fractures. Using CFD (where a flow network made up of channels was utilized), laminar viscous two-phase (water and gas) fracturing fluid flow via pores and fractures in a continuous domain between the spherical discrete elements was characterized. THM computations on small cohesive granular specimens that simulated rock under plane strain compression were performed in non-isothermal conditions. Initially, the rock specimen was made up of spheres of various diameters that had a single injection slot and no pre-existing micro-cracks, faults, or bedding layers. The effects of the temperature difference between the rock matrix and the fluid being injected, the fluid's dynamic viscosity, and the amount of gas present in the rock matrix on the initiation and spread of a single hydraulic fracture were the factors to be examined in-depth in a series of small-scale hydraulic fracturing simulations.