I've never seen snow in Sulani either but don't use mods or cc. I quickly checked The Sims Fandom site and found this section on climate:
"If The Sims 4: Seasons is installed, Sulani will have slightly different weather compared to most worlds. Namely, all weather types are higher in temperature, with winter only going as low as cool. There is a new weather type only found in Sulani called "monsoons". Monsoons are extreme thunderstorms that are stronger than normal thunderstorms in other worlds but happen for a shorter period of time. Monsoons only occur randomly during late summer to late fall.
Snow is also not present in Sulani, but Sims can use the weather-controlling machine to temporarily make snow appear."
I don't remember ever hearing about "monsoons" occurring in Sulani, so I learned something, lol. Unfortunately, though, the snow does sound like it has to be mod related. I know MCCC is a huge mod so if that's the cause, perhaps a simple setting change will solve the issue for you. Of course, all you can do is pull them and try to track down the culprit.
