Will skies be clear over southern Ontario Wednesday night?
Mostly cloudy skies are likely, except that occasional breaks in the high cloudiness (moving northeastward ahead of a low pressure trough which is south and west of the Great Lakes) may allow the brightest stars and planet (Jupiter) to become visible from time to time and give the impression of partly clear skies over some locations.

Will skies be clear over southern Ontario Tuesday night?

Mostly clear skies are expected overnight, except for some scattered low-level clouds that will probably be in the sky occasionally, resulting from some low-level moisture which is forecast to be over some areas of southern Ontario (especially south of Georgian Bay) during the night (illustrated below for late evening).

Wednesday night: clear skies, due to big high pressure ridge over southern Ontario (illustrated below).

Will skies be clear Tuesday night over southern Ontario?

Skies are likely to be mostly cloudy during early evening over most regions, due to low-level moisture flowing across southern Ontario regions south and east of Lake Huron and Georgian Bay (illustrated below for late evening) and passage of a cold front, but there will most likely be clear skies over various regions from time to time and after about midnight, especially toward morning as the cold front (causing the uplift and cloudiness) moves south of Ontario.

Will skies be clear over southern Ontario Sunday night?
Mostly clear skies are expected during early evening, followed by increasing high cloudiness caused by increasing moisture at jetstream level (illustrated below for late evening), except for southwestern regions where the high cloudiness is likely to be covering most of the sky by sunset.

Will skies be clear over southern Ontario Thursday night?
Clear skies are expected, caused by a high pressure ridge spreading over southern Ontario overnight (illustrated below for late evening) and air temperatures not cold enough to cause lake-effect cloudiness (except for some scattered low-level clouds that may appear over some regions southeast of Lake Huron and Georgian Bay).

Will skies be clear over southern Ontario Wednesday night?

Mostly clear skies are expected, except for cloudiness over regions south and east of Lake Huron, due to low-level moisture extending downwind from Lake Huron (illustrated below for late evening). As well as low-level clouds, some high jetstream-level clouds may also be visible after sunset but are likely to move east of southern Ontario by mid-evening.

Will skies be clear over southern Ontario Sunday night?
Skies will probably be mostly clear during the early evening over most regions except for southwestern regions, where high cloudiness is likely to be apparent by sunset. Elsewhere, high cloudiness is expected to spread eastward over southern Ontario during the evening due to mid and high-level moisture (illustrated below for early evening)  ahead of a low pressure storm developing west of the Great Lakes.

Will skies be clear over southern Ontario Saturday night?
Mostly or partly cloudy skies are likely over most regions, due to frequent periods of low-level cloudiness caused by very cold air and extensive low-level moisture flowing southeastward from Lake Huron and Georgian Bay (illustrated below for mid-evening). Enough breaks in the cloudiness will likely allow the full moon to be easily visible occasionally and give the impression of clear skies. Skies over southwestern regions (south of and not close to Lake Huron) will most likely be mostly clear.

Will skies be clear over southern Ontario Friday night?

Mostly cloudy skies are expected, due to lake-effect clouds south and east of Lake Huron and Georgian Bay caused by very cold air and widespread low-level moisture (illustrated below for mid-evening), except for far southwestern regions (south of Lake Huron) where clear skies are expected.

Will skies be clear over southern Ontario Thursday night?
Mostly cloudy skies are expected, due to high-level moisture flowing northward over southern Ontario to the north of a low pressure disturbance south of the eastern Great Lakes (illustrated below for mid-evening). The high cloud may allow bright moonlight to be visible, especially near the northern edge of the cloud shield.

Will skies be clear over southern Ontario Wednesday night?
Mostly clear skies are expected over southwestern regions, but partly clear skies are expected elsewhere over southern Ontario due to lots of low-level moisture (illustrated below for mid-evening) causing some cloudiness over regions south and east of Lake Huron and Georgian Bay.

Will skies be clear over southern Ontario Tuesday night?

Clearing skies are expected around sunset over far southwestern regions, while skies are likely to remain mostly cloudy over Lake Ontario regions and the GTHA during most of the evening until cloudiness moves eastward later in the evening.

By about midnight, the cloudiness is likely to be east of southern Ontario, leaving clear skies after midnight except for some occasional mid-level clouds.

Will skies be clear over southern Ontario Friday night?

Partly clear skies are likely, due to some low-level cloudiness that may appear occasionally over regions south and east of Lake Huron and Georgian Bay, caused by low-level moisture flowing southeastward across southern Ontario (illustrated below for mid-evening).