Abstract: The silo level indicating system includes a plurality of temperature indicating sensor units placed on the outside wall of a silo at vertically spaced positions. Each sensor unit and an adjacent portion of the surrounding sidewall is thermally insulated from the atmosphere so that a sensor unit is responsive to the temperature on the inside of the silo at the thermally insulated wall portion. The air within the silo above the level of material is at the same temperature. Thus, in a comparison of the temperature within the silo opposite each sensor unit to that of a reference sensor unit situated at the top of the silo, so as to be above the uppermost level of the material in the silo, a temperature differential between the reference sensor unit and a compared sensor unit indicates the presence of material at or above the compared sensor unit.