I just saved one sim from Grim after she collapsed from freezing. She was on the street in front of my sim's house and my sim convinced her to group up. It would take too long to walk back to my sim...
I guess it will be hard to balance. Either this sort of thing happens or nobody ever dies, making weather effects kind of pointless. I don't mind the odd sim having bad luck and kicking off, I just don't like the chain reaction of all the other sims rushing to witness the death and dying themselves.