Negative temperature in summer

[JonPak]

Hello Guys, The weather temperature was about +20 celsius. How it's possible that RC pro controller showed me negative temperature -2,2? I also saw -10, just don't have screenshot. Also had a night flight. The air temperature was +18 Celsius, but I also saw negative temperature. Is it normal and how to explain it?

 

[jaja6009]

Your image shows a temperature box with the highest and lowest temperature.

If you notice on the RGB image there is the metal racking system to the left that juts out.
Metal has a high reflectivity, low emissivity.
The metal is reflecting the cold sky, going on an angle that matches the same angle you are to the panels.