"Microwave" is a big range, from 1 to 1000 GHz. Satellite TV is in the ~10-20 GHz range, but I believe there are frequencies where clouds and rain are more transparent.

Edit: https://en.wikipedia.org/wiki/Microwave_transmission#/media/...

So I guess the goal would be to pick one of the high points on that graph that also wouldn't wreck havoc with telecommunications.