So how do you rock seasonal plaid without looking like you're about to build a log cabin while hunting a grizzly bear? Here are a few ways to keep your plaid city-appropriate:
1) Dress it Up:
Plaid is a pretty inherently casual pattern, especially when made from a thicker flannel cloth, as is wont in the colder months. However, this doesn't mean your whole outfit has to be way laid-back to match. Try keeping a bit of formality by wearing a plaid button-down under a blazer. I suggest a thicker wool fabric for the blazer to match the heft of the plaid. A tie and a pocket square seal the deal with a look that is definitely business casual, rather than redneck.
2) Don't Wear Jeans:
This is one of your easiest options. Instead of reaching for your favorite beat-up blue jeans, go for something a bit sharper, like some dark chinos. Those black and red buffalo check flannels that are so appealing look great with a pair of black chinos, while some of your lighter options will pair well with khaki's, or even some winter whites. If you do go for jeans, opt for a dark, dressier pair rather than your beat-up 501's.
3) Pay Attention To Fit:
This doesn't mean only wear super slim fitting plaids, but to know the fit of what you're wearing and treat it appropriately. A heavy, looser flannel shirt that you can pick up at your local thrift store will look way better used as a light jacket (say, over a sharp white tee-shirt, or even a turtleneck sweater) instead of trying to pull it off as a dress shirt.
4) Tuck It In:
This is a huge one. I'm definitely not saying that there is no style or class in an un-tucked casual shirt, but the loose plaid shirt is definitely a cabin-ready look. You can feel much more appropriately dressed hitting the city with your tails tucked. Again, though, pay attention to fit, and avoid billowing at the waist or sleeves.