People who know about Red-eared turtles please help.?

I have two Red-eared turtles that I've had for about 6 now. And I enjoy them and clean their tank once a week but I'm beginning to feel bad for them because I think they should be able to experience a real pond with other turtles, fish, frogs and other aquatic creatures. So I've been thinking of releasing them into a really beautiful pond in a cemetery(so it's safe). Although I live in New England so needless to say it gets cold out (into the teens) during the winter and I don't want them to end up dying, so would they be OK? The pond is filtered and I've seen multiple turtles and frogs etc.