I have been lucky so far having been able to avoid getting soaked in rain. I did get caught up in a torrential downpour with hail on Sunday afternoon during the last 3k of my run. I had knonw there was a strong chance of this happening, I could literally smell rain in the air, moments before the heavens opened. It felt like a "storm chaser" run.
I have to say, I found the rain very refreshing, I even stretched out my hands at one point to fully "soak in" the experience. The hail on my face was not too nice but made me run harder, as if fighting the elements.
Priceless experience! Would I do it again? If I can avoid it, probably not, but if it happens, it will not panic me any more. And sometimes it is just nice to do something completely crazy!