Why is the temperature difference between sunny and rainy days greater in winter?

There is a knowledge point to understand: when warm air from the south is dominant, the weather is generally sunny, and when cold air from the north is dominant, it is also sunny. The areas where cold and warm air flow meet are generally cloudy and rainy and snowy. Generally, cold and warm air is pushed around. As the saying goes, either the south wind overwhelms the north wind or the northwest wind overwhelms the southeast wind, and the intersection of the two is always rainy, snowy or cloudy, which is called warm and humid airflow. Cold air is dominant in the north in winter, and it is often cold in sunny days. When there is a warm air from the south pushing northward, the water content of the warm air flow is high, which is connected with cold and hot, and the air is dewy, so it often rains or freezes into snowflakes, so it will not be too cold in rainy days in winter, but it will be cold in sunny days, and it will be even colder in sunny days after snow, because there is another truth that "snow is exothermic and snowmelt is endothermic", and the opposite is true in summer!