The following policy regarding the cancellation of games applies at all levels:
If a game has been cancelled in advance (i.e. posted to the web site, and allocators and coordinators notified) then nobody gets paid. If the weather is questionable the umpires should check the web site before heading to the park to be sure, even if they have not directly heard from the umpire allocator.
If everyone shows up but game does not go on for whatever reason (weather, forfeit, etc) then umpires get paid half.
If game starts but but is terminated part way through then umpires get paid in full.