It really depends on where your antenna for the Sirius/XM is located. If it has an unobstructed view of the southern (or SSE) sky, chances are you'll have reception. Any little thing can block reception though - the camper, the truck cab, etc. As you get further north the satellites will be closer to the horizon so even some ground based things can block you like mountains.
Sirius/XM doesn't have as many satellites in the sky as the GPS systems do, but then again you only need to "see" one of them to get reception unlike GPS.