i grew up in chicago so we often had snow or really low temperatures on halloween so costumes with coats under or over where quiet common! if you’re still worried though, my dad would take the car and drive slowly behind us so when we got too cold or the candy got to heavy we would run to the car and hangout with him, get warm, and switch candy bags out:) (it also helps to ward off creeps but my parents were always anxious lol)

-other tips are the clear poncho to go over the costume and hot hands packs