Every time it rains mildly, I can hardly, if at all, see it through a glass window. If I open the window, I see just fine - and it can be raining hard enough to require an umbrella for a short walk.
The windows are fairly good noise-blockers, but are otherwise 'fully' transparent to visible light (as far as I can see). I also notice the effect to be stronger at night, but can't see much even under an intense street lamp.
So what is it about such glass that's transparent to visible light yet blocks off light reflected from raindrops? Or vice versa - what change does light undergo post-reflection that is responsible?