Check the weather forecast often. If rain is expected for Friday, try to paint on Thursday; if much rain is expected Thursday and Friday, paint on Wednesday.
If you painted during rain, please go back to the field later to check on the lines, and if necessary lay down an extra layer of paint (not during games.)
In case that it rains continually Wednesday, Thursday and Friday, you'll have to paint on Saturday or Sunday (after games, if they're not cancelled) so as not to lose the field layout. And repaint again on Thursday or Friday.