Cold weather, in Colorado? Nah!
LOL, Ok so here's what we do. First, my girls NEVER want costoms that cover ankle to neck, wrist to wrist. So, what I do is get their costumes one size bigger. So, they can wear them comfortably OVER sweats, jacks, or sometimes coats! Nothing like a lovely winter wonderland... on Halloween night! Yes, it's happened! This way, they can still be whatever they want, but we can adjust for weather. Now, if by some miracle, it's not cold enough for a coat underneath, the costume is a bit loose. Some pints in the right place, or a ribbon tied tighter here or there, and problem solved.
Don't look at me! I'm just the passenger!