Generally if wait til they are fully feathered they should be ok to go outside.
I have lost a few that I have put out early.
So I give them as much chance as possible.
This what I was told one time. And pretty well holds true.
A cold wet poult is usually a dead poult.
I have hatched a few poults but have only had one drown. I would put marbles in their waterer. Will help them if one would fall in. Also they are shiny so that envourages them to peck.
Usually I will hatch chicks to keep in with them to teach them to eat and drink. If don't have any to will...