Nights with clear skies and weak winds are common in the western Mediterranean area when pressure gradients are weak, usually associated with anticyclones that have their center over southwestern Europe. In such conditions, local factors predominate and nights are calm, with possible intense cooling in valleys and plains. Fog, dew or frost could appear. This study analyzes, through the application of some selection filters, the characteristics of stable nights during the period of 1997-2005 in the agrometeorological station of Gimenells, located in the eastern half of the Ebro basin. It shows the typical evolution of wind, humidity and temperature in stable conditions, identifying its principal directions and relating them to the topography of the Ebro basin.