Abstract: A thermal probe (10) for averaging temperature fluctuations over a prolonged period is formed with a temperature sensor (22) embedded inside a solid object (12) of a thermally conducting material. The solid object is held in a position equidistantly spaced apart from the interior surfaces of a closed housing (16) by a mount (14) made of a thermally insulating material. The housing is sealed to trap a vacuum or mass of air inside and thereby prevent transfer of heat directly between the environment outside of the housing and the solid object. Electrical leads (24) couple the temperature sensor with a connector (26) on the outside of the housing. Other solid objects of different sizes and materials may be substituted for the cylindrically-shaped object to vary the time constant of the probe.