GTA: Liberty City Stories -- Unlocking snow effects

[Seldomseen]

You know the 'Car Salesman' side mission? Now, I understand that to see snow in Liberty City, one needs to reach or beat Level 9 of Car Salesman. However, I was wondering one thing: Is the snow a permanent fixture in the game's weather cycle, or does it only last for a limited time (i.e. the duration of the side mission or the duration of the game before your next save/arrest/death)? Also, I managed to get to Level 10 before I failed the side mission; Do the snow effects become more pronounced when you pass levels 9 and 10 or do appear pretty much the same as they do in Level 9?

Also, another question: Does the game occasionally lag on you? For me, sometimes I'm running along and for half a second (it's a short but noticeable half second), Toni kind of freezes. The game continues at normal speed after that. It also happens virtually every time I wipeout off a bike after crashing into something. And as for load times, are they as frequent and unnecessarily long (particularly during cutscenes, when all that loads sometimes is just Toni walking away from some building!) for you as they are for me?