Today in Philadelphia it is 48 degrees and pouring rain.
Why not take the C3 out and test it out. The key things I was thiking about during my rain ride were:
Effective fog-blocking on the Shield / Pinlock System - Very effective, riding today would have been a mess without the pinlock system. Even some of the best fog-free coated shields would have been put to the test today. In my experience there are many shields form many brands and you don't get a good feel on how they perform until the temperature comes down and the humidity goes way up.
Leakage around the Shield Gasket / Seals - I was highway riding as well as doing headchecks at about 75mph. More than once I felt slight cold air come in, but it was nothing drastic nor did I get hit in the face with any rain.
Leakage through Vents at Speed - The top vent on this guy in monsterous and flows a good amount of air and vents directly to the top of the head, so it was no surprise that I felt a little *tick* of water come in here and there with it open. Once I closed the top vent I had no issues.
Wicking of water from the neck to the liner - I rode for about 30 minutes and I would consider this helmet's ability to block the elements from underneath and around the neck as above average. I am less than concerned with this though as going for a longer trek in similar conditions or colder conditions would have me throwing a balaclava on to bridge the gap between collar and neck roll.
I had very high expectations for the C3 in the rain. Schuberth had done so many other things correctly with this helmet, that it only stood to lose points in my book for an average showing in full precipitation. It is, remember, one of the more expensive investments as far as helmets go.