I've got a question about the special rules that apply to terrain in BTB. For example in the Northern Wastes, one of the special rules that applies is "Bitter Cold". If I then look up "Bitter Cold" under the Weather Rules, then there is a further listing of special rules ("Snowstorm", "Deep Snow", "Wintery Chill", "Ice Field").
Now my question is this: do those last 4 special apply to the entire gaming table or only to specific pieces of terrain, e.g "Deep Snow" only applies to pieces of terrain with snow modelled on them? And will the "Snow Storm" be there all the time?