hot hot weather

Iam using a 5wt 8' rod with 5wt wff line and am getting 20-25ft cast most of the time.would going to a 6wt wfline help me or is that going to mess up what I've got now.I went out late this afternoon on a small local lake that the city han stocked for a kids fishing tourney about 3 weeks ago but it is so hot down here nothing was biting .no one was having any action ,not even the bait fishers :(

the line should be ok. when it hot fish deep

When it's this hot, fish deep, fish very early in the morning and/or very late in the evening. As a general rule, fish are a lot like you and me, they are most active when the temperature is most tolerable.