If you don't have snow or ice to deal with, regular slicks with no tread are fine in the wet. Unlike car tires bicycle tires won't hydroplane. Living in Vancouver our roads are mostly wet from Nov through Mar so I get lots of experience riding on wet roads and my tires have no tread. I obviously go slower on corners in the wet and if it's close to 0C, slower yet on corners. Hitting the odd patch of icy or compact snow while going in a straight line isn't normally an issue unless there are deep ruts.

To those who have some experience with studded tires what does a decent set of studded tires cost? I could see keeping a set on a spare wheelset to try occasionally. I know I could search for this info but if someone here can provide a ballpark number I would appreciate it.