Will skies be clear over southern Ontario Thursday night?
Clear skies are expected over most regions, except for high cloud that is likely to spread northward over southwestern regions before morning caused by the leading band of high cloud ahead of the remnant of ex-hurricane Harvey (illustrated below for early Friday morning).

Will skies be clear over southern Ontario Wednesday night?
Partly or mostly clear skies are expected for several hours during the evening over most regions, after daytime clouds diminish after sunset and before widespread low-level and mid-level moisture moves southward over southern Ontario around midnight (illustrated below for late evening).

Will skies be clear Tuesday night over southern Ontario?
Skies are likely to appear mostly cloudy during the evening due to lots of mid-level and jetstream-level moisture (illustrated below for late evening) which is forecast to gradually diminish by early Wednesday. The moon and brighter planets and stars may be visible during the evening and give the impression of clear skies in some regions where cloud cover becomes thin.

Will skies be clear over southern Ontario Sunday night?
Skies are likely to appear mostly cloudy due to increasing high and mid-level cloudiness, although the moon and brighter stars and planets may be visible and give the impression of partly clear skies during the evening.

Will skies be clear over southern Ontario Saturday night?
Mostly clear skies are expected except for increasing high cloudiness over southwestern regions by sunset and during early evening, caused by high-level moisture which is forecast to spread eastward over southern Ontario overnight (illustrated below for late evening).

Friday night: clear skies are expected (except for smoke aloft).

Will skies be clear over southern Ontario Thursday evening?
Mostly clear skies are likely over most regions, except for some mid-level cloudiness during the evening over regions from the GTHA westward and north of Lake Erie, due to mid-level moisture which is forecast to be over these regions during the evening (illustrated below on the charts for 500 and 700 hPa levels). Also, some jetstream-level clouds may be visible over most regions, due to the jetstream south of Ontario and jetstream-level  moisture moving over most of southern Ontario overnight (illustrated below for late evening).