I've been commuting for about a year and ride also in the rain if I have to but not often. I noticed my headset makes a cracking noise if I lift the bike up at the front and turn the bars from side to side about 60 degrees or more each way. There's no noise if I just turn a little bit. I read on Sheldon Brown that the lower headset bearing gets a lot of grit into it if you ride in the wet.

Should I pull it apart and pack the bearings with new grease?