Sorry I can't really give advice for your area. I'm in Sub-tropical zone (south of Tropic of Capricorn).

About the Impatiens...

Impatiens grow really well here, so maybe you could make a hot-house of some kind. They love humidity. They seem a very tropical plant for your region? I'm not sure plants like that can survive your changing temps there?

Maybe organize a green house for those types of plants. Takes up very little room if done correctly.