Weather affecting monster stats / abilities?

Would it be hard to make it so that (occassional and / or random) weather changes make monsters harder or weaker? "Screen goes darker, monsters become harder" sort of thing ... I found such a thing lacking in so many games, and I think it would be killer to have it implemented!

I don't think it's been confirmed anywhere that PoE would have day/night cycles or random weather. Even if those were just cosmetic then they would certainly be really cool. Not to say that the weather would change as you were playing but each time a new area was instanced a type of weather would be applied. Battling hordes of monsters in a rainstorm could be pretty epic.

If they did have random weather and it realistically affected gameplay then that would be simply amazing. Characters (especially those with more armor) would be slower in the rain. Wet bows would be less accurate. Monsters could have a preference for the day or night and be spawned accordingly.

It does not have to be complicated. It does not have to deal with weather, if it would be time consuming to implement - curse or boost affecting players or mobs, triggered upon opening chest or corpse searching, with some visuals changing, like dense poison cloud covering part(s) of the screen for a long time, or distorting the view / bluring, would do it.