I agree with Steve. "Winter rest" really means "no nitrogen" more than anything else. The "more light", "cooler temperatures", and "no water" go right along with that, but are really "side effects" ("co-effects"?):

Essentially all of the food an epiphyte sees come about with rain cascading down through the forest canopy. Most "resters" live in areas where there are distinct seasonal changes, most often "wet" and "dry" (although is some instances, "dry" means nothing more than less than an inch a week). Cooler, drier air is often accompanied by less cloud cover, as well, so the obvious observances are in temperature, light level and rainfall, even though it's really the result of all of that, that matters.