Draw or sew faces onto the sleeves of coats, the palms of mittens, and the tops of hats. Familiar characters are best—kids will always agree to putting on a coat if it’s not just an article of clothing but, rather, a friend.
Similarly, animal-themed hats, coats, and gloves will work more effectively than standard attire.
A warm, plush Halloween costume can provide an emergency alternative to an unpopular parka. He’ll be more inclined to stay in his lion suit or cat hat.
For hat haters, try earmuffs. They’re less restrictive (and less warm), but at least they keep the ears cozy. And they come in duck, bear, and penguin forms.