My understanding is that they will cancel it or postpone the start if there is a high likelihood of severe weather like hail/dangerous lightning/tornados. If it is just raining hard, the ride will go on. I don't mind riding in the rain, but we do ride some smaller roads, and if it keeps raining, I am worrying about some of those flooding. It is supposed to let up at some point tonight and then start up again tomorrow afternoon sometime, so hopefully we can get the ride started in good weather and finish as much as possible before it kicks off again tomorrow.