I'm not sure how old your car is or what the differences are between recent and older, mine's '86 and I've driven it in heavy rain and torrential rain with the hood up and always been impressed by how little rain gets in. Misting up can be a problem but the wipers work well and I have NO qualms AT ALL about using it in these conditions.
In August in Suffolk my wife and I encountered the heaviest rain I have seen, an absolute cloud burst, I got a wet arm when a bus passed the other way and splashed water up between the side screen and the door. There was a loud squeeling noise which sounded like the fan belt slipping whenever we were particularly deluged but it never missed a beat and we were reasonably dry at the end of the joiurney too. Go for it, you'll be fine!
Regards
