The rain? You don't know commitment until you've been out running when there's a couple of inches of snow on the ground, it's about -3C and it's chucking it down. Coming from Scotland the concept of not doing things because it's raining is somewhat alien, you'd never get much done at all.
I'm not running much at the moment because of a back issue but when I do go running outside then it doesn't particularly matter whether it's raining/snowing/windy or not - a little bit of rain doesn't hurt.