question for those in the know.
I lived for years in KS and other tornado alley areas w/o issue but now have a wife and daughter that freak out when it storms.  As a result, I will soon have an inground concrete storm celler (6x8) with metal door and vents.
If I put some of my smaller potted figs (1-7 gallon) in there to overwinter will I need to heat it or will the concrete/underground be enough insulation?  zone 6b here in NW Arkansas  CAN get to single digits but most commonly teens.
Thoughts?

I don't know what the temperature would be.  I guess it would depend on how deep it is buried and how deep your frost line goes.  Keep in mind that before refrigerators people dug root cellars.  If I remember correctly being underground kept the area cold even in the summer, but the temperatures would stay above freezing in the winter (if the doors insulate and seal properly).  

But that is a very good idea! 

I've successfully used a root cellar (cold cellar) to overwinter figs in zone 6b/7a for a couple years now.  In Arkansas the only concern I might have is that it may not stay consistently cold enough in there to keep the figs dormant.  Here in the northeast that doesn't seem to be a problem.  I stick the pots in there well-watered and don't even water them all winter (using plastic pots...I did water halfway through the first winter but I don't think it needed it).  Humidity in a cold cellar stays relatively high (80-90% I believe) as long as ya have a dirt floor so that cuts down on watering needs.

I can hear my wife banging on the door now shouting I knew you loved the figs more

Meghan  about 6 foot under with about 2.5 feet above.  frost line cant be too deep

good points Tim,,,  anyone else?

Sdog, LMAO,, I had similar thoughts....  ;o)

If you want to insulate the doors you could always add some to help keep the temperature above freezing.  Just like people insulate their garage doors.  But your right.  Should be more than deep enough to keep them protected through the winter.

Strudeldog, you are too funny.  What is it with the men on here thinking their spouse is going to be jealous of a tree.

Actually would more concerned about not cold enough but am thinking the steady temp would be ideal. Only other concern i might watch is mice getting and eating the bark.

I wouldn't worry overly much about low temps in your part of the country.  The "door" on my the cold cellar I use is simply a few 2x6s propped up against the old door frame.  I imagine that on cold nights (this year coldest was 9 degrees, previous year was 11 degrees) the temps dip into the 20s.  Those who store their pots in an unheated garage or a detached shed likely see temps dipping perhaps into the teens.  

Absolutely no way it will get too cold. The winter temperature will be near or slightly below the average annual temperature in your area, something in the 50s, 40s at coldest. This assumes totally buried. Soil temperature at 6ft is nearly constant all year and runs near ave annual air temperature. Too warm is more concern than too cold unless the top is open. They grow citrus in unheated pit greenhouses in areas colder than AR.