@a086
The Basic diagram is the « sensitive weather » at ground level that is predicted by the model you have chosen. If you want to know the temperature which is forecast aloft, there are 2 ways:
Just switch to Airgram. You will know the temperature, clouds and wind according to altitude levels in hPa.
Or press your mouse right button to display a small window and select Soundings. The sounding forecast is shown for your location. The red curve gives the temperature profile, the blue one being the dew point. The wind speed and direction are displayed too. If you move vertically the horizontal axis you get the temperature according to altitude. Then you may scroll the time slider to see the temperature changes in next hours or days at the altitude you want.
I think it’s better to keep Basic diagram as basic as it is.