I've found that humidity readings are considerably lower for an outdoor sensor that's located near a structure with solid surroundings (cement, wood, asphalt, brick, etc.) such as on the north side of the house under an eave. A location out in the yard surrounded by grass and vegetation gives higher readings (including dew point since that usually uses humidity for it's calculation). My wx website shows this on my "Charts and Graphs" page. I have two separate stations deliberately setup this way (one on the shaded north side with tiles/cement/brick surroundings) and the other station out in the middle of the yard with grass. Both stations have the digital type temp/humidity sensor chips.