i don't think the water has to be too cold. i might be wrong here but i believe showering in room temperature would do the trick as well, and if not it'd help ease into it
well yeah warm water is fine for your skin, i'm not saying anything a little above freezing cold water is bad for your skin and yes it can help with waking you up (if thats what you're saying) i just have cold showers because it wakes me up in the morning, a sudden shock to the system really, if you gonna do it you gotta do it right and go all out B]