Due to a recent inquiry regarding the warmth of skirts in winter months, I thought I would post some more of my own apprehensions with wearing skirts.
My house was 60 degrees this morning, due a gas main break late yesterday afternoon, which put our heater out of commission. Not terribly cold, but cold enough. Cold enough for me to pull on jeans, not the cute skirt. Not to say that it's impossible to stay warm in a skirt. Cold-weather options would include ankle-length skirts, though I'm not a huge fan. Without a slit, they can indeed be as warm as a pair of pants if made from thick material.
Tights offer some amount of warmth, but not enough to keep one warm during a snow storm. And, the short-skirt/tight ensemble poses a unique problem to someone would might have trudge through snow in -40 degree weather on a regular basis (which I may have to do later this winter). I just don't think snowboots look great with a skirt, and snowpants would be difficult to pull off without sufficient privacy. I personally opt for tights on Sundays, mostly because I can't stand to wear non-sandal shoes without some kind of sock. (I refuse to throw out the legging option, because I was pretty sure they were ugly in the 80s.)
I've done enough research to realize that not only has outer wear come a long way, but so has underwear. I suppose another option would be the lovely long-legged bloomers or full-length, panted slips worn in the 1920s. I suppose the closest thing we would have today is the secretive Moromon temple garments, though you have prove you're a member to actually purchase them online. If you're into the ankle-length skirts, my drama days are proof that petticoats and bloomers offer quite a bit of warmth to the wearer, but few styles today are petticoat-friendly.
I suppose the answer to the question is this: if you wish to stay warm while keeping with modern skirt styles, there is no adequate way to keep warm, so crack up the heater. Or wear pants.