Why would you introduce a non-native species to the outdoor environment? Chinese mantids are aggressively supplanting native species. I don't allow them in my gardens, where they do far more damage to my beneficials than anything else.

Bees and butterflies don't have a chance.

But, you didn't ask about that stuff.....temperatures that low may very well cause your mantids problems. The other issue of prime importance is the availability of a food source. They'll devour each other unless there's lots of other things moving around.