Choosing clothes for a winter wedding is just like doing so for any other wedding. Except for a few things you need to keep in mind:
Adhere to the dress code. This is often stated in the wedding invitation. A more formal event might warrant a tux for the gentlemen and a formal dress for the ladies.
Find out where the venue is. If you will be expected to spend a bit of time outdoors, then you’d have to wear something extra warm. You’ll have more options if the venue is somewhere indoors with heating, such as a hotel ballroom.
For autumn and winter weddings, it’s best to keep to cool and deeper shades such as green, blue, mave, plum, etc.
To keep warm, you may bring a wrap or stole or maybe even a fur cape to make it even more stylish. A jacket can be taken off in case it gets warm.
Of course, you can wear thermals and nobody can tell, just make sure you get something in a style that would be hidden under the cut of your clothes.
Kitten-heeled boots or heels that can keep your toes and most of your feet covered will be fine for footwear.