A tag or smart label including a humidity sensor, and methods of manufacturing and using the same, are disclosed. The tag or smart label includes a substrate or backplane with a battery or antenna, a humidity sensor, and an integrated circuit thereon. The integrated circuit is in electrical communication with the humidity sensor and the antenna or battery, and is configured to process a signal from the humidity sensor corresponding to the humidity level or value in the environment to be monitored, and provide or generate a signal that represents the humidity level/value. The humidity sensor includes first and second electrodes that are a predetermined distance apart, a humidity-sensitive material having one or more electrical, mechanical or chemical properties that vary as a function of the humidity level/value, and a water- and/or humidity-permeable membrane covering the humidity-sensitive material.