Galaxy S5 does not have Temperature and Humidity sensors, unlike S4. Samsung announced it and close to publishing decided not to ship it. It seems that the reason was the fact that these two sensors could not work along with water-proof feature.
S Health app has ability to measure body temperature but its API is hidden at this moment. It means that we have no clue if it measures temperature via external devices (Gear) or it can measure it using heart-rate sensor. Also we don't know if it can measure air temperature (probably not).