Willing suspension of disbelief

The Scene:  MB and I are watching season three of Buffy, the episode "Amends". After a near-hour of characters bitching about the heat in the Southern California (fake) town of Sunnydale, a lovely snowfall interrupts a big dramatic scene between Buffy and Angel.

MB:  What the hell? What is up with the snow?

VBG:  It's a romantic moment.

MB:  It doesn't make sense.

VBG:  Christmas magic, then?

MB:  I still don't get it. What is it supposed to mean?

VBG:  Well, snow sometimes symbolizes purity, or a clean slate.

MB:  I still don't see how it relates.

VBG:  There are demons living under the Christmas tree farm, and you're worried about a little snow?