Last Friday night at 6300' on Roan High Knob, the low temp was 2*F, and there were strong, gusty winds. I hung in my Speer hammock, with Speer Snugfit, Speer Top Blanket, Molly Mac Gear Canvas Hammock Sock (not insulated)... and no tarp.
FourDog hung with no tarp over his Molly Mac Gear Canvas Hammock Sock in MN at -15*F, but the winds were light. I had a Speer Witner Tarp with me, just in case, which I was thinking of hanging as a one-sided wind break.
Darby looked at me like I was crazy when I told him what I was using for insulation, and that I did not rig my tarp! (The ratings for the Snugfit and Top Blanket is in the 20s.)
I was toasty! It's amazing what a lightweight, windproof, breathable, canvas hammock sock can do in cold weather!