Something seems very odd about this. Either you're putting us on, I suspect, or confused.
1- You're right, that is C shaped. Perfectly. With perfectly straight line s at the edges, and perfectly straight borders. Even if it were man-made
rain, it is unlikely you would see something like this, except from water dumped from PIPES.
2- You can not even have man made rain without clouds, save hanging PIPES in the sky.
3- If you are sincere, it is possible this is a glitch on the website, not the computer.