Yeah, it's not the running in the cold, it's the waiting around beforehand. Monumental I think is small enough that the runners don't have a hugely long wait? And NYC wasn't that cold, but the wind was piercing. For the four and a half hour wait before my start, besides what I ran in, I had two throwaway fleece tops (one hooded), a Tyvek coverall, a reflective mylar poncho, and eight chemical hand warmers, and I was chilly but pretty much okay since I snagged a spot that was mostly sheltered. But there were a lot of people who were shivering for hours.