I woke up this AM to find that our large round top window in our family
room had cracked during the night. It was 20-30 below zero last night
in Minnesota. I was wondering if the cold weather can cause this. Our
house was built in 2002 so the window is still actually pretty new. If
the cold can do this how does one prevent it from happening?

The chances are pretty good that it was a one-time event, caused by
a combination of thermal stress and settling of the house over time,
and maybe flexing of the wall and window under wind-load or a
flaw in the window-glass. If you've got some heat source
that's heating the window unevenly, like a spot-light or hot-air vent
aimed directly at the glass, you might move that.