A system can include a sensor assembly and a wellhead flange sized to receive the sensor assembly. The system can also include a seal that can be positioned between the sensor assembly and the wellhead flange for sealing the wellhead flange from an external environment. The system can also include an inner coil that can be positioned within the sensor assembly. The inner coil may be able to communicate wirelessly with an outer coil that can be positioned around the sensor assembly for transmitting data and power with respect to the wellhead flange. The system can also include a sensor positionable in a through bore of the wellhead flange. The sensor can be coupled with the inner coil for transmitting and receiving data and power with respect to the wellhead flange.