Hello dart frog guy,
From what I have read I think keeping a barred tiger year round outside in Iowa would be a bad idea. It appears that although it is possible that their range extends that far north there have not been any confirmed sightings? Either way, the enclosure required to hold it would have to be significantly large, deep, and detailed as to include all their methods for dealing with both heat and cold and I don’t think we know all of them. Maybe it can be done but it seems unnecessarily risky.