Wow. If you are not familiar with winter gardening, do indeed check
out extending the harvest. Then do a little reading up on the works of
Eliot Coleman:

Four-Season Harvest: Organic Vegetables from Your Home Garden All Year
Long

http://www.amazon.com/gp/product/189...712600?ie=UTF8

Brief summary: covers shift your garden 1 zone south for each layer
(unheated hoophouse, floating row cover)

I'm in zone 5 and when outdoor temps are 0-10, it can be as high as 40
in the hoophouse. When the sun really comes out, it can get as high as
50 (temps always lower at night though). I have 3 months in the dead
of winter when life is tough for the plants, and 3-4 weeks either end
of the season when plants are just fine under cover.

Bottom line: hoophouses are great for beginners, not a huge investment
in time, material or infrastructure. If you really want to get into
winter gardening but want to start small, I suggest a couple cold
frames to get you going.