Surely I’m not the only one who has noticed this. When it snows at night, I’ve seen that the sky is really a bright grey, and you can see much better than when it’s not snowing. What’s up with that?
I think it’s because snow means there will be cloud cover, clouds reflect lights better than the clear sky.
Also when it is foggy or cloudy: The city lights are reflected back by the fog, snow etc. A clear sky does not reflect the light back.
Also, fresh snow reflects something like 88% of the light that hits it back into the air, where it can illuminate the underside of the clouds.