i just slept out in the florida december winter, my whole body wrapped up in a sleeping bag. was pretty cold because it's so humid in florida.
had a 40 degree mummy bag kaufland, 1.75 lbs
wind/water resistant/polyester fiber batting/mega light microfiber fll with hood/polylining
it was okay. throughout the middle of the night i threw on a quilt over the bag. wasn't bad, only when i woke up was i freezing but kept moving around in the sleeping bag to stay warm and and the sleeping bag was pretty good for insulation. a better sleeping bag like 20 degrees/30 degrees and i probably wouldn't have needed a quilt. sleeping outside in the cold is very nice if you can keep warm and it's not too humid
florida winter just is kind of rough because everything gets wet in florida, there's humidity all year round -.-
http://www.amazon.com/Kaufland-Superlite-Mummy-Sleeping-Green/dp/B00IS8DGAW 