iacas said:You'll want a better phrase than soft. Soft implies "tacky" to me. Think about this: which does your cue slide over more easily: a block of wood or a sponge? The harder one.
Anyway, I've never really played pool in the summer, but I've never needed anything. If I am a little damper in the summer with added humidity, I imagine I may buy a glove.
So, "a glove" is my uneducated answer. Uneducated because I've never had to find a way to keep my cue sliding through easily, not even with powder.