When I took my images for this topic, I used the flash for some of them. In these images you can see the raindrops are lit up and frozen in motion in front of the camera. The reason that you can see this only in these photos is firstly because when the flash is engaged, the camera automatically makes the shutter speed as short as possible. This is to avoid the camera from taking in too much light from the flash and overexposing the image. This makes it possible to see the raindrops as individual shapes as opposed to blurred entities because a faster shutter speed eliminates motion blurs. Secondly, the light obviously illuminates the raindrops before the camera.

Below is a comparison between one image taken with flash and the same image taken without it. These were taken seconds apart and so this demonstrates the effect of the flash on the appearance of the light.