Eric has a set of rules he uses. He has posted them in the past. I believe if it's going to be below 3x degrees he will cancel. At Marion County they can shoot under cover and it really helps with the wind. There is no protection from the wind at ACC.
As a former match director, I can appreciate it if Eric doesn't want to run the match when it's super cold; it's considerably less fun to be a match director when you're freezing.