Rain rain go away, come again some other day. Except I'll probably be running then too. How about you just come back when I'm injured? At least that way I won't feel too bad about having to go swimming and worrying about lane politics for three weeks.
Yes, skin's waterproof, but my running gear isn't. Yes, once you're out in it it's never as bad as you imagined it would be, but nobody ever wants to go out in it in the first place. Yes, it can cool you down on a hot day, but in the winter it makes your fingers numb and your ears hurt.
Rain is stupid. Nobody's ever turned up to a race and said "Oh great, it's raining". Rain makes your clothes heavier and it makes surfaces slippery. It makes your super-duper new touchscreen GPS watch go crazy. It makes evil white van men drive through puddles and soak you with dirty gutter water.
At least once your rainy run is over you can experience a sweet sense of relief when you step indoors, right? Wrong! Now you have to hang your wet clothes all over the house to dry out and find somewhere special to put your sodden shoes. And you were going to wear those tomorrow for that ten miler because they're your favourite.
Then you have to get in a shower which is basically like more rain.
The weather forecast is covered in clouds! My only hope is that it gets so cold it'll snow instead.
The forecast for tomorrow is good*
* assuming you're dying of thirst in the desert