Will skies be clear over southern Ontario Tuesday night?
Partly clear skies are expected over eastern parts of southern Ontario, due to lots of upper-level moisture (illustrated below for late evening) while mostly cloudy skies are likely over southwestern regions.

Will skies be clear over southern Ontario Sunday night?
Partly clear skies are expected, due to widespread high clouds caused by lots of jetstream-level moisture which is forecast to be over southern Ontario overnight (illustrated below for late evening).

Will skies be clear over southern Ontario Saturday night?
Partly cloudy skies are likely, due to extensive high cloud drifting eastward from thunderstorms over the western Great Lakes region (and can be seen below on the mid-afternoon visible satellite image) and illustrated on the forecast chart below (for Saturday evening) although the high cloud will occasionally be thin enough over various regions to allow skies to appear mostly clear.

Will skies be clear over southern Ontario Friday night?

Skies are likely to remain cloudy over southwestern regions overnight, and clear over easternmost regions of southern Ontario (generally near, north of and east of GTA) and partly cloudy to varying degrees over other regions, due to some mid-level and upper level moisture which is forecast to be over southern Ontario overnight (illustrated below for late evening).

Will skies be clear over southern Ontario Thursday night?
Clear skies are expected, except for some scattered mid-level clouds over some regions caused by a region of mid-level moisture which is forecast to move southward over southern Ontario overnight (illustrated below for early Friday).

Will skies be clear over southern Ontario Wednesday night?
Clear skies are expected, following Wednesday afternoon's cold front, except for some low clouds that could appear occasionally, due to clouds remaining after development and then dissipation of thunderstorms.

Will skies be clear over southern Ontario Monday night?
Clear skies are expected, except that regions near, north and east of Toronto may have some scattered  high cloud appear occasionally during the first half of the night until some jetstream-level moisture moves south of the province.