Yah windcovers make so much of a noticeable diference. I smoke in the freezing temp. of SLC Utah every weekend and every wednesday and if i did not have a wondcover, my coals would not even be able to stay lit.
I can't even light QL coals during the winter at all. They just don't light up all the way cause it' so damn cold outside.
I think my smoke is just as thick outside, and it's easy to keep my base water freezing because, well, it's damn frigid cold outside. If the water wasn't constantly in motion it would freeze completely in 20 minutes!