Too cold for comfort?

It is two weeks before we leave for our trip.  I checked the Weather Channel for temperatures at Glacier and found a big surprise.  Nighttime temps are in the 20's.  Burrrrr!  This could change our plans.  Sure, we have a furnace, but would our water lines freeze?  Glacier may have to be another trip at an earlier time.  We will make that decision on the road.