Earlier studies have demonstrated that the Northeastern Brazilian region (NEB) has the most abundant solar energy resource of the Brazilian territory due to its geographical location, and its environmental characteristics. However, the spatial and seasonal variability was little evaluated. This work investigated the surface solar irradiation variability and trends based on a statistical analysis of the ground data acquired in automated weather stations operated by the Brazilian Institute of Meteorology. A data quality control procedure was accomplished according to WMO criteria to avoid suspicious data. The results pointed out a remarkable variability in seasonal and annual scales. The cluster analysis provided five regional patterns presenting quite interesting temporal complementary regimes for the incoming solar irradiation. The surface solar irradiation achieves the highest values in the Southeastern area of NEB and the lowest in the Western area during the austral summer. The annual and seasonal trends of the surface solar irradiation were investigated using the Mann-Kendall method and the Sen technique. The surface solar irradiation in the Southeastern area of NEB is decreasing by 50 Wh/m(2)/year since 2008. On the other hand, it is increasing around 40 Wh/m(2)/year in the semi-arid area at the same timeframe.