When my dad, uncle, and I were regularly attending high school playoff games, we were pretty much a walking Carhartt ad at the colder games. My dad and I wore their insulated overalls and jackets, and my uncle wore their insulated coveralls. Layers were the order of the day; if it was cold enough, I'd wear a Carhartt hoodie under the coat, but I usually had at least a sweatshirt under the jacket. Add a good pair of insulated boots and gloves, plus a good stocking cap, and you should be good to go.
One other thing to consider--bring something to sit on for insulation. If you're in the older concrete/rock stadiums, you can get by without it, but the newer stadiums with 'loomnum stands are giant heat sinks that will flat out suck the heat right out of your hindquarters. Anybody who watched HS playoff games in Stillwater prior to the renovation can attest to that...(Heck, it might still be that way; I just haven't been up there since then.)
One other thing to consider--bring something to sit on for insulation. If you're in the older concrete/rock stadiums, you can get by without it, but the newer stadiums with 'loomnum stands are giant heat sinks that will flat out suck the heat right out of your hindquarters. Anybody who watched HS playoff games in Stillwater prior to the renovation can attest to that...(Heck, it might still be that way; I just haven't been up there since then.)