Winter is corduroy and moleskin trouser time, trousers being the principal application for cotton in a man's tailored clothing for cool weather (there are both corduroy and moleskin jackets but I am not fond of the former as the wales prevent a coat from hanging as well as it ought and there are plenty of good alternatives without that problem; the latter is rare though it makes up as a nice cold weather shirt jacket).
Useful and economical as it is generally, cotton is less practical in the cold because the smooth surface of the typical weave means it does not trap air next to the skin where it can warm up and help keep the wearer warm. That characteristic accounts for the popularity of woolen flannel, for example, as well as moleskin (everywhere but the United States where it is relatively hard to find) which is cotton that has been brushed during the milling process to give it a nap.
Moleskin comes in a variety of weights to accommodate a range of temperature, with 15 to 20 ounces (450 to 600 grams) appropriate for moderate to sub-zero weather. Corduroy comes in a similar range of weights and also a variety of wales per inch, wales being the series of ridges that give it its distinctive texture, that can range from about two to as many as twenty. And though no corduroy is ever formal enough for business, as the number of wales increase so does the formality of the cloth.
The popularity of both corduroy and moleskin is principally due to its relatively low cost, as the best of it is roughly half the cost of suiting quality wool from one of the better English mills. But both materials excel below tweed jackets where their surface interest adds character to an ensemble.
Cold weather cottons are best in Autumnal colors in my opinion. Besides the usual greens, tans and browns try rust and corn yellow. There are reds and blues too, though those are probably better for the pub than the field.
Corduroys and moleskins. At least one pair of each should be in every man's cold weather wardrobe.