From working superman many years, I can confirm it is stated in the ride's manufacturer standard operating procedures as well as the SOP for the operators that it must not be operated when temps fall below 55 degrees.
After many years of working at theme parks, i can say that many rides, including coasters that are pretty much identical, operate and behave differently when it comes to temperature. Superman does not run very well in cold temps. Sometimes it's scary to watch it crawl through.