Why does rainfall make slanted streaks on the side of the window of

Question

Why does rainfall make slanted streaks on the side of the window of

Answer 1

This is caused by the wind blowing it, the slant on the window of rain can indicate what the wind direction is.

Answer 2

This is because of the wind direction. If the wind blows at a particular angle relative the surface of the window, you can expect slanted streaks when there is rainfall.