Most people find that a warm water enema can be held more easily than a cold one.
I use a very warm enema when I want to fill myself with the maximum amount of water possible. I use a cool water enema when I need to force out water and material that is stuck in my bowel. The temperatures given are that of the water as it is poured into the bag. It cools off some before it gets into the colon. Don't try to judge temperature with your fingers, they're too unreliable.