Many marathons are held when the temperatures will be in the 50s to 60s, and the bulk of runners will be comfortable wearing shorts and a short-sleeved shirt or singlet (no sleeves). So if you’re shopping for marathon-day attire, this is your best bet. But since you never know what Mother Nature will dish up, and you may be training for months ahead of time in colder weather, it’s a good idea to also purchase tights, long-sleeved shirts, a hat, gloves and jacket/vest.

See:

Outerwear
Shirts
Shorts
Socks
Tights