The Canon 7D has quite nice weather sealing - "Canon considers the weather resistance of the EOS 7D to be slightly better than the EOS 5D Mark II and 50D cameras, but not as robust as the EOS-1D series." (Chuck Westfall, Canon USA)

What this basically means is that you can not worry about shooting in rain. I wouldn't take it swimming, but you might be able to get away with a dunk in a pool.

The 50mm f/1.8 on the other hand, has essentially no weather sealing. It is almost all plastic, and has no seals or gaskets to keep water out. In my personal opinion, it is such an inexpensive lens, I wouldn't worry about it much. I wouldn't want water to enter into the lens, then into the body of the camera though, so don't get it too wet. This lens is not "resistant" at all. It is more like a sponge :)

So to sum up, unless you are really worried about the very inexpensive lens, I would just shoot away as normal. If you are really worried, I would either upgrade to a weather sealed lens(and filter if necessary) or do what I do when shooting without a weather sealed kit - just leave it under my jacket until I take a shot, then wipe it off a bit before putting it back away.