A thermal well temperature monitoring assembly with high dielectric strength capability is disclosed consisting of a low relative dielectric constant material in a continuous structure that does not have any air voids or pockets. The low relative dielectric constant structure of the thermal well has at least one internal cavity having an end region. A thermal sensor is at least partially located within the at least one internal cavity. The thermal sensor has one or more wires extending out of the end region of the internal cavity. A first low relative dielectric constant potting material encapsulates at least a portion of the thermal sensor within the internal cavity to remove air voids that decrease dielectric strength. A second low relative dielectric constant potting material fills at least a portion of the end region of the internal cavity to provide mechanical ruggedness and environmental sealing.