I wrote a simple Windows Console (Command prompt) application which uses Exiftool to add EXIF 2.31 weather related tags to photos for cameras which may lack this functionality:
- Ambient Temperature
- Humidity
- Pressure
If you can obtain a log of these weather readings for a particular area (for example a local weather station) near the location you took the photos the app will attempt to match the readings using the log and photo date and time values. Further info, source code, compiled app for download and sample images/weather log can be found the WeatherTag GitHub Page: https://github.com/josemoliver/WeatherTag (https://github.com/josemoliver/WeatherTag)
Thanks to Phil for maintaining the excellent EXIFTool.