Humidity and temperature are considered to be important factors in designing comfortable seat surfaces. A small number of studies have attempted to address this; however the methods used were limited regarding the placement of their sensors. This study aimed to design a sensor array system to investigate changes in humidity and temperature for eventual use in the study of factors affecting sitting comfort and incontinence detection. The system was subjected to three types of experiments: sensor response verification, thermal radiation testing and in situ trials. The variance in output within each type of sensor was small (±3.5% and ±0.3°C) and there was no apparent change to the variance in output of the sensors, when used in air or on a foam cushion loaded with a 50 kg sandbag (p > 0.1). In the human sitting experiments, although the profile from sensors under the thighs and ischial tuberosities were similar, the magnitude of change could be affected by position and body mass of the subject. This was especially noticeable with the sensors under the coccyx. These results support the use of multiple sites for sensor placement over the use of a single site when studying these parameters at the interface between subject and seating material at the seat base.