After the dark clouds in summer, why does it rain more on a very white day?

The rain in summer is mostly frontal rain (the rainstorm in the afternoon in summer is convective rain), and the temperature in summer is high and the air is heated. At this time, if there is cold air blowing, then at the interface between cold air and hot air (imagine that this is a curved surface, which can be translated by a half parabola, or you can imagine the shape of waves), water vapor will liquefy when it meets cold, and condense into small water droplets, which can be scattered or radiated, making the sky look darker. Because water droplets scatter or refract the most, the sky is the darkest. However, because the water droplets are still in the process of condensation, there are not many water droplets falling, and the joint of the cover will pass quickly, so the dark time will not be too long. After the intersection passes, the sky will become brighter. Because there are clouds in the sky, the light injected into space will be scattered many times in the space between the clouds and the ground, making the sky look brighter. The rain formed at the junction of the front and the rain formed at high altitude will fall behind the front, so the rain after dawn Frontal rain mostly falls on the cold front, only after the cold front, so it is the rain behind the front, which is why it becomes cold after raining in summer.