Reconstruction of a three-dimensional temperature field using interferometry is presented. The reconstruction procedure involves projection data that are recorded in the form of interferograms. The physical problem addressed is Rayleigh-Benard convection in a horizontal layer of air at a Rayleigh number of 3.48 x 10(4). Experimental results of the reconstructed temperature field in the range of Rayleigh numbers 10(4)-10(5) are not available in the literature. Interferometric projections of the temperature field in the fluid layer are recorded using a Mach-Zehnder interferometer. Four different view angles are considered. The three-dimensional temperature field is reconstructed from two orthogonal projections and three different reconstruction algorithms. The correctness of the reconstructed temperature field is tested by a cross-check against the projections from the remaining two view angles. Results show the formation of a three-dimensional cubic roll pattern for the thermal field in the fluid layer This has been interpreted as flow associated with a buoyant plume rising from the hot surface. The fluid is seen to be cooled at the top boundary and descends all around the central plume.