To reduce the cost of carbon capture, transportation and eventual geologic storage at potential geologic sites future sequestration plans envisage the locating of power plants at potential geologic sites. The implication is that the injection temperature of flue gas will be typically those encountered in combustion power plants. This, obviously has a geomechanical consequence considering the fact that heat transferred from the aquifer to the low permeability cap rock will cause excessive pore pressure build up due to poor pore pressure diffusion characteristics of these rocks. While these low permeability rocks are required to provide stratigraphic trapping mechanisms such excessive pore pressure build up can result in compromising the geomechanical integrity. This paper has used heat transfer theories and geomechanical concepts to obtain steady state temperature distribution in cap rocks for temperatures ranging from 50 to 800 °C. In so doing, cap rock critical temperatures for tensile and shear failures have been established for a potential on-site gas injection into saline aquifers.