Inflight BBQ's,
When maintenance has the wx radar turned on on ground, it's most probabaly in test mode. I fly an old piece of junk with an AVQ10 wx radar, with that in test mode, it basically only tests the screen, not the TX. I wouldn't worry about it too much, but would avoid walking in front of the nose dome....I don't know what the test mode does on newer generation airplanes/wx radars.
I don't agree with having the wx radar off on the ground. Reason for that (call me nuts) is that on our old system it actually scares off the birds on the runway. If we depart from a runway with birds around it, we usually leave the thing on. Believe it or not, but they all disapear off the runway.