Well I find that View Invalid
Reason is, it will never rain just on the windows, It rains
and when it does it will run off the brick work and then onto the window....
You need perfect circumstances IE
Not too windy,, Not near the sea,,, Not near a main road
And So on..
I have cleaned in the rain and have had windows that come up good but not all...
So I would say its down to the work you have...