I've read some other reviews of the Netatmo system that questioned why you would even need the device, considering the availability of basic temperature and humidity data on weather apps. (treehugger.com)
Global humidity data at very high altitudes in the stratosphere and above. (eso.org)
Climate Consultant (just above) provides temperature / humidity data overlaid on a Psychrometric Chart for many locations. (builditsolar.com)