should I keep it the same when winter arrives , because our winter is cold and we have snow event in many times
Yes you keep and the winter,it is necessary ,one example the cold nights with no cloud in the sky ,and no wind ,there is temperature inversion the cold air it will enclave in the tube and the temp sensor it show lowest temperature for the correct,for this reason it is necessary to work the fan with half speed at 6 volt ,for unenclave the colder air where it have enclave it the tube,and the temps it will increase.
If there are not temperature inversion the winter night you will see ,if you have open the fan ,and when closed the fan you do not see any differents at temperatures.
Where are you come from ?