Answer: This is more of a guess based on what I already know about liquid in certain temperatures but I would say it would have to be related to the blood having a harder time congealing due to the molecules moving faster because of the temperature. You probably already know that atoms move faster in higher temperatures as opposed to cooler ones, therefore the process of congealment and essentially transitioning from liquid to solid would be easier/quicker in cooler temperatures where the atoms in and around the wound would be moving slower.
