Will skies be clear over southern Ontario Sunday night?

Skies are likely to be clear by sunset over most regions, except for regions near and north of GTA, where low-level moisture (illustrated below at 850 hPa level) will most likely cause some low-level clouds to be visible for several hours following sunset.
Later, mid to high-level clouds may appear over most regions of southern Ontario before sunrise as a result of high-level moisture (illustrated below at 500 hPa level) which is forecast to move eastward over southern Ontario. By then (early morning), fog is likely to develop over most regions of southern Ontario as a result of the humid air over southern Ontario during Sunday afternoon and night and diminishing winds by midnight.

Will skies be clear over southern Ontario Friday night?

It looks like skies will be mostly clear by sunset and then mostly cloudy before morning, due to moisture moving eastward over southern Ontario ahead of Saturday’s low pressure trough. The chart below illustrates the forecast mid-level moisture a few hours before sunrise, but moisture is forecast to be increasing at all levels overnight.

Will skies be clear over southern Ontario Monday night?
Partly cloudy skies are likely over most regions, caused by a region of mid-level moisture which is forecast to move over southern Ontario (illustrated below), as well as high and low clouds that may appear from time to time, although skies may appear to be clear over some regions due to the appearance of the bright Hunter's Moon.

Will skies be clear Sunday night over southern Ontario?

Mostly clear skies are likely except for occasional periods of partly or mostly cloudy skies over some regions, caused by low-level moisture (illustrated below for late evening) which is forecast to move eastward across southern Ontario during the evening.

Will skies be clear over southern Ontario Thursday night?

Skies will likely be mostly clear by sunset and clear overnight, except for some evening low-level cloudiness over regions north of GTA caused by low-level moisture moving southeastward from southern Ontario (illustrated below for late evening) and except for increasing high-level cloudiness that may appear over southwestern regions before morning (ahead of a low pressure trough that is forecast to develop west of the Great Lakes).

Will skies be clear over southern Ontario Sunday night?

Skies are likely to be mostly clear by sunset  and then clear overnight, except for some low clouds that are likely to diminish during the early evening as low-level moisture (illustrated below) gradually moves southward from southern Ontario during the evening.

Will skies be clear Saturday night over southern Ontario?
It looks like partly clear and occasional cloudy periods is the best description for the forecast, since lots of low-level moisture is forecast to flow southeastward over southern Ontario, causing cloudiness over some locations, but more persistent mid-level moisture (illustrated below) is expected to cause more persistent cloudiness especially over regions south of Lake Huron.