I have a fig planted inground that froze completely back to roots last winter.  New growth came late so it is only about 1" diameter.  Overnight temp is forecast at 27 F.  Will the main branches survive that without damage.  I suppose I could get something over it but not the coverage I want to use.  I've just been dragging on getting it completed.

I would say it will be just fine.  But if it's a tree you REALLY want to survive, I would do what it takes to protect it and not take chances.

Winter hasn't even started. More cold coming. Wrap it the right way. One night of cold shouldn't kill branches, not even sudden cold. I wrapped my trees today, it took an hour and a half.

I think your tree will be fine. I used to freak out about frosts and now I welcome them to force dormancy. That being said - if it gets really cold you will loose things. What is "really cold"? Ahhh that's what we're all trying to figure out. What's hardy and what's not?

Thanks for the help.
Looks as if tomorrow will be a lot warmer than tonight as far as getting it covered.
Tomorrow evening and the next several will be even colder though.
I'll have to do a little work tomorrow.

Charley, if you can drape anything over them, it will give you a bit of a buffer. Two weeks ago, the forecasted low was 31, but it got down to 24. It zapped most of the leaves from my trees.

Rafael, For some of us, winter has started...

I am also considering protecting an in-ground black mission that I grew from a cutting and planted this year. I received good advise to keep it out of the ground for two seasons before planting it, but now it is well rooted and very vigorous in ground. I am concerned about how to protect it though. We get some wild temperature swings in the winter here, like from the 20s to the 70s in the same week some times. I am thinking burlap around the tree surrounded by leafs or pine needles encased in wire mesh and capped with an upside down pot. I have seen this method in pics mostly from northern growers. Can this successfully be done in zone 7b or 8a? I think any tarp or plastic enclosure would fry the tree. My small unheated greenhouse would get up to 100° last winter with the door closed.

Beware the voles and bunnies.

Charley, you said your main branches are new growth. 
Are they still green or have they lignified?  If green they can be damaged.   27F is Ok for older hardened main branches. 
Also how accurate are the forecasts in your area?  Over here it is + or -8 degrees.

Generally the forecasts are pretty accurate on temps.  Morning forecasts of evening lows are very good and pretty acccurate for several days out.  Cold temps arrive from west or northwest direction this time of year.  Whatever St. Louis or Indianapolis gets will be here in a day or two at the most.

Most branches have lignified and turned nice and brown.  Those are still small diameter however.

Thanks for the help and advice on what to look for.