A temperature sensor assembly for measuring temperature of a fluid in a conduit, the assembly comprising a temperature sensor and a thermowell housing the temperature sensor and embedded in a wall defining the conduit. The thermowell has a face for interfacing the fluid that is substantially non-intrusive relative the conduit and a groove that extends radially inward of the thermowell housing to minimize the cross-sectional area of the thermowell body proximate the location of the temperature sensor.