The Slano blato landslide is one of the largest landslides in Slovenia with a volume of more than 1 MIO m³. In dry periods the landslide behaves as a group of several slow moving landslides. In wet periods it moves mainly as a viscous earth flow with occurrences of rapid mudflows. The transformation from the slow moving landslide to the much faster mud flow depends strongly on the combination of the rainfall infiltration at the landslide territory itself as well as the water influx from the bedrock. Instead of monitoring the ground water level and horizontal ground inclination in the short life time inclinometers, a new monitoring system, using soil suction measurements with the Watermark sensors was installed in 2007. The soil suction and the ground temperature data are taken continuously, together with the data from the weather station and the GPS position of sensors. The measured data are available online, together with the TV camera shots observing the landslide surface 24 hours/day. Field monitoring data show clear connection between rainfalls, soil suction and the development of the surface soil instabilities.