As long as the seam is dry when you start, I don't think a little moisture will effect the silicone. It's pretty much water repelant in any form, whether mixed with mineral spirits or straight out of the tube. I seam sealed my Cloudburst2 tent while it was drizzling and it did fine.
“Light thinks it travels faster than anything but it is wrong. No matter how fast light travels, it finds the darkness has always got there first, and is waiting for it."