Well, I still don\'t think that actual rain will be possible with the cavern ceiling being relatively close to the first level. Apart from that, the second and lower levels are even closer to the lower floor of the upper levels, meaning that clouds wouldn\'t form. Therefore, I think it\'d at best be mist and dew, not actual rain.
As for ths snow:
from art/gui/zodiacs.xml
Hoarfrost has thickened to resemble something that some races refer to as snow. Some ice flakes fall from the small vents in the cavern roof and settle on the upper levels, which begin to melt off as Novari draws to a close.
This strongly suggests that there is no actual snow. However, with temperatures this low, the absence of snow also hints at the absence of rain in warmer temperatures, since snow is just frozen rain.