Using meteorological data spanning more than ten years in Oman, radial basis function neural networks were developed for estimation of the solar radiation and clearness index for any location in Oman, given its longitude, latitude, altitude, sunshine hours and month of the year. Data generated for 25 different locations were then used to plot contour maps for monthly average daily solar radiation and clearness index over Oman. These maps will serve as a much needed reference for design and performance evaluation of solar energy conversion systems in this region.