Sweaty hands

I use baby powder on my palm and in my glove

A lot pf pros wipe the grip and hands before a shot. 
 
If you decide to use a glove, take it off between shots and while 
putting, so it does't get soaked through.    
  
Some say they use rain gloves. 
 

Use fresh grips if you have old grips. 

I wear two gloves.  In the summer I'll wear up to 8 different gloves during the round.  I've also resorted to wearing long sleeves in the summer.  I used to wear sweat bands but they just end up getting soaked by the middle of the round and would need to carry multiple pairs to stay dry.  The long sleeve stay dry material is pretty good at wicking sweat away.  The long sleeves also prevent me from having to wear sunscreen on my forearms.  The sunscreen would run down onto my hands and make the grips impossibly slick.

I was thinking about buying a rosin bag but baby powder should do the trick as well.  It's a big problem for me in the summer.

Art's point about the rain gloves is also good.  They are better at absorbing the sweat but even they will need a refresh or to dry out some as well.  I have a pair of them in my rotation of 8.

When I'm coming to Myrtle Beach and it's a bit too hot and humid, I do use rain gloves and it works for me!