Visibility Facts
In weather lore, the saying 'clear moon,frost soon' is actually right. When the moon is clear and night visibility is good, the atmosphere is clear and cloud free.

The surface of the Earth will cool rapidly by radiation. If no wind exists and the temperature is low enough, frost may well form.

hazy halos
When it is very hazy, and it looks like the Sun (or the Moon) is hidden behind a halo, this is actually evidence of a layer of cirriform clouds - high ice-crystal clouds.