Get Different Outfits for Different Needs
In most areas, the temperature does not go from hot to cold overnight. There are days when the weather may be warm, then mild, then cold, then mild again, etc. You need to be prepared for whatever Mother Nature may throw your way. Get a series of dog outfits that you can switch between to keep your pet warm in any climate. A light shirt, a medium sweater, and a heavy jacket should be enough to suit most situations.
Consider the Material
The material that your dog's winter outfits are made of will determine a number of things – how long the outfit lasts, how well it covers the body in winter, how easy it is to clean, how well it holds up to damage, etc. Consider how your dog spends his time in the winter and use that to judge which materials will be best for your outfits. If your dog spends a lot of time outside, you may need a thick jacket to stand up to the twigs and other debris in the yard. If your dog spends most of his time inside, a simple knit sweater may hold up well enough.
Worse comes to worse, you can always keep a variety of outfits on hand made from different materials so you have options to choose from.
Measure the Length
The generic size of a dog outfit may not tell you all you need to know about it. Sure, this will help you determine if your dog can get into the clothing, but it won't tell you where the bottom of the outfit will land on your dog's body. Measure your dog to make sure that no part of the outfit is going to come in contact with his “lower area.” More specifically, you want to make sure the clothing will not get dirty when your dog uses the restroom. Long dogs like dachshunds can usually wear just about anything, but dogs with shorter torsos may need modifications to make their winter clothes work.
Avoid the Itch
Do you have certain pieces of clothing that naturally make you itch? This may be from the material they're made out of or the tags they have along the collar. Either way, it would be safe to say that you avoid wearing these clothes for very long. Your dog may feel the same way about certain winter outfits. If you can see that your dog is annoyed by one of the outfits you purchased, avoid buying something with the same material or same embellishments in the future. This way, your dog will be happy to wear the awesome winter attire you selected for him.