Gregory,
The Magic Pie should be fine, but I would suggest you purchase the external controller version, as it would be more suitable for use in your extreme temperatures.
The motor and controller both generate their own heat, so the internal controller version is much more likely to overheat and cut out when it gets too warm. This is due to the additional heat that will build up within the sealed hub assembly, because there are no vents to allow a flow of air to help keep it cool.
Alan