If rain is in, then I assume it's something they've only recently, or are still currently, implementing into the game, right?
There has been quite a bit of gameplay footage, with new features such as day to night transitions, but I have yet to see any rain. I am interested to see how GT5 does the rain. The rain looks pretty realistic in WIP shots of Codies F1 2010, and with Kaz being a so-called 'perfectionist', it will be exciting to see how good/realistic the rain and other weather effects look visually and how they will affect the driving.