Guild Wars 2

are weather effects area triggered or time triggered?

like the rain in the oasis of the new area?

Hmm…I’ve noticed some areas have rain at certain times, but not others, so I would guess it is not area-triggered.

I haven’t noticed any rain in the Oasis, though. Maybe I just missed it. /shrug

I think one of the centaurs in the new area mentions that the centaur shaman has created permanent rainfall in the oasis, thus saying how the oasis was formed.

the rain is event-triggered (help the centaur shaman secure the oasis), the sandstorm is time-triggered.

Maguuma of GW1 naturally went from lush jungle to barren desert. IIRC, Drytop was that way heavily as well.

Oasis could likely be natural, but the Centaurs keep it active with magic as well.