Will skies be clear over southern Ontario Sunday night?
Mostly cloudy skies are expected, due to lots of moisture at all levels, except for brief periods of mostly clear sky that could develop over some or most southern regions especially during early evening. The illustration below shows the forecast location of mid-level moisture during the early evening.

Will skies be clear over southern Ontario Saturday night?
Mostly cloudy sies are expected, except for mostly clear skies near, north and east of the GTA during the early evening, and then cloudiness is forecast to spread eastward across those regions by late evening. (The charts below illustrate the low and mid-level moisture during mid-evening.)

Will skies be clear over southern Ontario Friday night?

Mostly cloudy skies are likely, due to lots of low-level moisture which is forecast to be over southern Ontario overnight (illustrated above for early evening), except for some breaks in the low overcast which may appear occasionally during the evening, especially near Lake Erie and western Lake Ontario.

Will skies be clear over southern Ontario Wednesday night?
Mostly cloudy skies are likely over most regions due to lots of low-level moisture (illustrated below for mid-evening) and then increasing high cloud before morning, but skies could become partly or mosttly clear occasionally over some regions.

Will skies be clear over southern Ontario Monday night?

Partly clear skies are likely to develop over some regions, but mostly cloudy skies are likely most of the time over many regions south and east of Lake Huron and Georgian Bay, due to lots of low-level moisture flowing southeastward from the lakes (illustrated below for mid-evening).

Will skies be clear over southern Ontario Saturday night?
Mostly cloudy skies are expected over most regions overnight due to extensive low-level moisture flowing southeastward from Lake Huron and Georgian Bay (illustrated below for mid-evening), although partly clear skies may develop occasionally. Partly clear skies are likely before morning over most regions as the northwesterly flow backs to southwesterly, but increasing mid-level cloud is forecast to move eastward over southern Ontario.

Will skies be clear over southern Ontario Wednesday night?

Lots of high cloud is expected, especially during early evening, but clear periods are likely to occasionally result in skies becoming mostly clear.