How does temp and humidity affect the legacy signal?
None at all as far as I know. I've never heard that mentioned.
The legacy signal to the track is a rather low frequency at 455 Kilohertz. So not sensitive to say a fog or anything. But the signal from the CAB2 to the base is 2.6 Gigahertz, and a fog would affect that if say you are down the block trying to communicate with the base.
Temperature might affect the frequency stability if it’s really really high like 130F or so.