And if the worst happens and you do crash in the rain the slickness of a wet road seems to impart less road rash than a dry one. But seriously my only concern riding all winter up here in the rainy NW was having tires tough enough to resist punctures as wet roads seem to allow you to pick up a lot more glass and junk than dry ones - so I was actually riding in effect slicker tires than my summer ones all winter long with no problems. None of my tires have any tread pattens, but the winter ones are made of harder rubber so don't "stick" to the corners as well.
The biggest things are to be careful of any metal - like sewer caps, and painted lines on the road both of which become very slick when wet and slow more than normal for corners. Since its probably a TT crashing seems pretty unlikely on the straight sections.