Synthetic jet is a compact heat transfer technology which is suitable for cooling of miniature consumer electronics. High mixing and entrainment characteristics make it the promising technique for active flow control, mixing enhancement and drag reduction. This experimental study investigates the heat transfer performance of an axisymmetric synthetic jet under the influence of Richardson number. Infra-red thermography technique is used for convective heat transfer measurements. A cam-follower mechanism is used to drive a diaphragm, which pressurizes the fluid in the cavity to generate axisymmetric synthetic jet at Re = 76 − 338, through 10 mm circular orifice hole. Synthetic jet is impinged orthogonally on a heated vertical flat surface kept at orifice-to-surface spacing of 50 mm, to achieve Richardson number in range of 0.9 to 20. All experiments are performed at fixed stroke length (L/D = 5 ). Cooling performance is evaluated with reference to natural convection, using enhancement factor and time-averaged Nusselt number. Enhancement factor is found to be maximum in vicinity of impingement region and decreases radially. The radial extent of enhancement factor signifies the ability of synthetic jet to sweep over the surface after impingement. The rings of enhancement factor imply the extent of perturbation of thermal boundary layer by sequence of vortices.