Unfortunately, I don't have experience growing Cedar. But, I would imagine they are similar to most other pines. My advice: do whatever. Pines are extremely hardy trees. Unless heavily diseased or flooded, they will not die. We once had a live cut Christmas tree survive indoors with just water until St. Patrick's day! Besides, during the winter the trees are dormant anyway. The important thing is to make sure it is planted by June. That is when the real growth and nutrient action happen. So, if you happen to get some nice weather, go ahead and set it outside. The cold won't hurt it. If not, be sure to set it out in spring time.

Also, when planting, be sure to make sure all roots are pointing downwards. If pointing up, they can supposedly "J-root" and begin growing upwards, which is thought to kill the tree. On the farm we just use an old paint stir to push all roots down into the hole. Also, you could even snip the roots a bit. Pruning the roots (if not done in excess) can help encourage root growth in the Spring.

Hope this helps!