A regionalization of different characteristics of the solar resource is performed for Uruguay and surrounding areas (Southeastern South America). The input information consists of daily satellite estimates of Global Horizontal Irradiation (GHI) generated in a regular grid using a low uncertainty empirical satellite-based model which was specifically adapted for the region. Clusters are derived from the climatological annual cycle of monthly irradiation and clearness index and, separately, from time-series of monthly variability. The solar irradiation variability in each cluster is compared with El Niño South Oscillation (ENSO) signal. A high negative correlation is observed between ENSO and solar irradiance, most predominantly over February to May and November to December, particularly for the latter. This means that in a strong El Niño/La Niña year, solar irradiation values for the November–December period in Uruguay will be smaller/higher than the climatological average. These results are in agreement with the ones obtained for rainfall in other studies.