WARNING: This page is about a different car, the 2011 Honda Pilot, 2010 Honda Pilot, and 2009 Honda Pilot. However, it is still accessible from the selected car via links, so may be relevant.
The capacitance of the humidity sensor changes by the adsorption and the evaporation of moisture. The resistance change of the humidity sensor changes the output voltage.
Fig 1: Identifying Humidity/In-Car Temperature Sensor Voltage Graph