I don't think it will rain on foggy days. Is there any scientific reason?

Not necessarily, there are two kinds of fog: one is called radiation fog; The other is called advection fog.

The radiation fog formed by radiation cooling mostly appears at night and early morning, when the weather is clear, the breeze is light, the water vapor near the ground is rich and stable, or the temperature is reversed. Especially in autumn and winter, due to the long nights, there are not many opportunities without Feng Yun, and the ground heat dissipation is faster than that in summer, which makes the ground temperature drop sharply, so that the water vapor in the air near the ground can easily reach saturation in the middle of the night, condense into small drops and form fog. Therefore, the appearance of this fog generally indicates a sunny day.

In the advection fog, warm and humid air moves horizontally, and after passing through the cold ground or water surface, the water vapor in the air is gradually liquefied by cold to form fog. Mao Mao's spring rain is often accompanied by this fog.