Thermidistat does not accurately record OD temp

[sparrow]

We recently installed a two-stage Bryant Furnace with a Thermidistat.
We notice that the outdoor temperature recorded by our Thermidistat is usually 9-12 degrees HIGHER than the actual outdoor temperature. Given that we live in the record-setting cold Northeast we're wondering if this recording is effecting the heat/humidity levels in our home.

We think the temperature differential is a result of the placement of the outdoor Thermidistat component. This component is mounted on the south side of the house (yes we occasionally get sun)and is somewhat shielded by the vinyl siding. Our installer told us that this is the only place where he could install the Thermidistat and that we shouldn't worry about the temperature differential. But then what's the point of being able to access the outdoor temp?

Any enlightening comments on this topic will be appreciated.