http://www.bbc.co.uk...atures/28355583
Basically the long and short of it is Fri/Sat increasingly hot (30+ both days) and Sunday is going to be a total lottery. With storms/showers they could be unlucky and get a massive hit with major downpour rain leading to a red flag, lightning, hail etc, or get lucky and have a storm passing by a mile or 2 to the south for example. Very much going to be a radar watching day on Sunday, but also worth noting that with storms, they can pop up out of nowhere, so we could see rain falling in front of our eyes before it even registers properly on the radar if 1 pops up and dumps rain on the track from right above it.
Either way, it'll be very warm still, so if it rains at any point, I'd expect it to dry relatively quickly once it stops, particularly once they get back running (though obviously the SC would stay out far too long, to the point where it's basically too dry for wets by the time they bring the SC in)