The type of weather you'll be working in will also have a big impact on both the exterior and interior of your jacket. When thinking about work jackets, most people envision brown or black cotton duck material, which is extremely popular for exteriors. This fabric is tough and easy to clean, making it a good choice in many cases. For wet and windy conditions, however, a nylon or polyester exterior might be more to your liking. They're not as rugged as cotton duck but will keep the wind and rain at bay. Interiors are made of a number of materials, and selection largely depends on how cold the weather will be. Down is warm, but when it gets wet will let you down. Polyester or synthetic isn't as good as down thermal-wise but works much better when wet. Work jacket interiors can also be made of flannel or wool—both very warm materials.