I thru-hiked the Appalachian Trail years ago...admittedly, I was walking, with a pack, not running...
If I was within sight of shelter (a rarity) I sometimes trotted, and stayed a bit dryer...usually I just walked on, smiled, and tried to find things to enjoy...
One thing I learned was that it didn't matter one whit if I got wet when hypothermia was not a factor...the only important thing was whether or not, once I'd enjoyed the rain, I had dry clothes in my pack to change into while I cooked my supper...
I think we undervalue the good feeling rain falling on us offers...kids instinctively experience it as something special and dance around in it...imagine that...
We could re-learn things from them...rain's nothing to fear...