I personally love spring and summer weddings. Even fall, but being a wedding professional I can certainly see the advantages to having a winter wedding. For me personally it's also a nice change in pace. The air is crisp, everyone is bundled up, and not a whole lot of time is spent outside anyway.
1.) More Venue Dates
Winter as you can imagine (especially here in NY) is not the most popular time of year for weddings. So if you're thinking of having your wedding in December - March , chances are there will be much flexibility for you to pick your date. Another advantage is that , if you're having your wedding at a multiple event venue, there very well might not be any other events that day. This means the grounds and building is yours for the night!
2. Less Stress over weather
Since most of the day is inside anyway, no need to worry about rain, wind and cold. The only thing to keep in mind is travel if there's snow of course. But other than that, there are no worries about switching where the ceremony will be, having to set up a tent etc. Provided there is no snow storm disrupting travel, mother nature is taken out of the equation!
3. Christmas Decor
Having christmas decor for your wedding is more easy and accessible then any other decor. Chances are your venue will already have it. It's also REALLY pretty in my option, and as a videographer/photographer I can tell you that lighting from neutral warm christmas lights, is extremely versatile for weddings. You could use it to light a subject, backlight a subject or just having it out of focus in the background like this picture to the left looks amazing as an addition to any photo.
4.) Snow in your photos
Not only it being on the ground, but especially if you have flurries on your wedding day, that could make for amazing pictures! Imagine your'e a bride who's lucky enough for that, and your videographer (myself perhaps) takes slow motion shots of you and your groom while it's snowing. Well that's just demo material right there.
5.) It's a perfect time of year for in warmer places.
If you're in FL, Georgia, or almost any of the most southern states, you may not have snow on your wedding day but chances are, there will be all around good weather. Picking your wedding day for February or March on a Florida day in my opinion is absolutely perfect. According the national weather index, Orlando is around 75 degrees average in February.