OK, if you see these negative temperatures in Satellite layer, it is not a bug.
It’s more obvious if you select INFRA + in Satellite layer. The temperature is that at top of clouds, not at ground level. It gives an idea of the altitude of cloud tops using infrared sensors of satellites. The colder the tops are, the higher the clouds stand. When this temperature is very low (with dark red color) it probably means a risk of cumulonimbus which give strong thunderstorms.
By the way these temperatures are not shown in Weather radar, just in Satellite layer.