Flow past a heated/cooled circular cylinder is computationally investigated in this paper. The presence of a buoyancy force arising due to a change in density alter the vortex shedding dynamics. The governing equations, Navier-Stokes and energy equation within the Boussinesq approximation along with continuity equation are solved using a hybrid FEM-FVM technique. In this work we focus on the minimum Reynolds number at which vortex shedding occur. In hydrodynamic stability literature, this value is most often termed as the critical Reynolds number, which is approximately 47 for flow past an unheated cylinder. This demarcation between steady and unsteady regimes of the flow changes due to surface temperature. Due to an increase in surface temperature the frequency of vortex shedding is known to enhance. We show that the nondimensional shedding frequency, the Strouhal number increases with heating and has a strong dependence on Prandtl number and Richardson number of the flow, which are a measure of fluid diffusivities and buoyancy force respectively. We also discuss the regime of complete suppression of vortex shedding due to cylinder surface temperature. © 2015 Begell House Inc.. All rights reserved.