Climate class describes the intended ambient operating range. It concerns the room around the appliance, not the temperature selected for the food inside.
What the observation tells you
A refrigerator suitable for a normal kitchen may not be suitable for an unheated outbuilding. The exact range must come from the rating information and manual for that model; another owner's experience is not a substitute. Seasonal changes can expose an unsuitable location.
A useful next step
Record the model, climate class and approximate room conditions when explaining a seasonal cooling problem. Do not add a heater inside or modify controls to compensate. Seek advice on a suitable appliance arrangement.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.