From the pic it looks like you have a roof mounted Vue, which is a terrible location for a temperature sensor. On a sunny day it will read high, on a cloudy day it will read low. If the location has changed please advise of the new location.
Stated on the gladstone web page: "Your readings indicate a solar heating problem. This means that the sun can shine directly onto the temperature sensor (or it's housing) and increase the temperature recorded significantly. This is often caused by the lack of a radiation shield, or the sensor is poorly sited. For information on radiation shields, see CWOP Radiation Shields, and information on siting, see CWOP Station Guide."