I wouldn't even try it in your location. If it's a rescue issue, sometimes there are dog rescue transports that would take a turtle, too.
Some people put those heat packs, the kind that hunters use to warm their hands in the fields and you can buy in Wal-Mart, in between the first and second box, if temps are low, but it's just too risky in your location.
:Can some one tell me the best way to ship turtles I live in Minnesota and it is getting pretty cold here? Or should I not do it at all in the winter?