PI Vagabond is a great jacket and while it is water resistant, I soak through in short order in a constant rain.

If I know it's going to rain I carry or wear a J&G waterproof breathable for $100.

http://www.bicycleclothing.com/

I consider their breathable helmet cover to be the best piece of rain gear I own. It makes all the difference.

I also own the waterproof (i.e, lighter but non-breathable) jacket and its much lighter but retains some moisture.