Prior to he very cold marathon weekend earlier this year, DW and I bought mylar blankets right off Amazon. We also went to Walmart and stocked up on throwaway blankets, hats, sweaters, gloves and handwarmers. As cold as the forecast was, we needed to be prepared, and since we were doing Dopey, we were. Those mylar blankets came in very handy on race morning. I'd go into the corral, form a little tent over myself and be quite confortable until I had to get up and move towards the start. Once the race started, we just threw away the other clothes as we warmed up.