Will skies be clear over southern Ontario Tuesday night?
It looks like some high-level cloudiness will be over most regions, although some periods of partly or mostly clear sky may give the appearance of clear skies, particularly with bright stars and moonlight shining through thin high cloud.

Will skies be clear over southern Ontario Monday night?

It looks like skies will be clear over most regions, except for southwestern regions where increasing cloudiness is expected during the evening. Upper-level moisture is forecast to gradually move eastward across southern Ontario overnight (illustrated below for late evening) and to reach the GTHA area around sunrise. So, for most regions, skies are likely to remain clear during the evening.

Will skies be clear Friday night over southern Ontario?

It looks like skies will become mostly clear, except for some cloudiness near western Lake Ontario and the GTHA, caused by a region of low-level moisture (illustrated below) that is forecast to remain over that area during most of the night and then finally move southward before sunrise. 

Will skies be clear over southern Ontario Tuesday night?

It looks like skies will become cloudy overnight, due to increasing moisture moving eastward ahead of a low pressure storm system moving eastward over the southern Great Lakes region overnight. Skies might be mostly clear at sunset, or may already be partly cloudy with high cloudiness. Increasing high-level moisture (illustrated below) is forecast to move over southern Ontario ahead of thicker cloudiness and will most likely appear as increasing high cloudiness during the evening.

Will skies be clear over southern Ontario Monday night?

It looks like skies will be partly cloudy over most regions as a result of a region of high-level moisture (illustrated below for the 500 hPa level) that is forecast to be over southern Ontario overnight and to cause some cloudiness over most regions.

Sunday night: mainly clear skies.

Will skies be clear over southern Ontario Saturday night?

It looks like skies will be mostly clear, except for some low-level moisture near and to the north and east of GTA (illustrated below) that will most likely appear as low-level clouds during the evening.

Will skies be clear over southern Ontario Wednesday night?

It looks like mostly clear skies are expected, except for some high-level moisture that is forecast to move southward over southwestern regions after midnight (illustrated below) and will probably appear as high cloudiness.

Tuesday evening and overnight: clear skies are expected over southern Ontario (except for southwestern regions where some increasing jetstream-level moisture may cause some high clouds to become visible several hours before sunrise).

Will skies be clear over southern Ontario Sunday evening?

It looks like skies may remain mostly clear for several hours after sunset, except for increasing mid and high-level moisture (illustrated below) that will appear as scattered or occasional mid and high cloud over most regions during the evening, and then cause cloudy skies by late evening or midnight.

Will skies be clear Thursday night over southern Ontario?

It looks like skies will be mostly clear, except for high-level moisture (illustrated below) moving southeastward over regions near and north of GTA and Lake Ontario that will most likely appear as high-level cloudiness. 

Will skies be clear over southern Ontario Wednesday night?

Clear skies are expected ahead of a building high pressure ridge.

Will skies be clear Tuesday night over southern Ontario?

Cloudiness over southern during Tuesday is forecast to move eastward and leave clearing skies during the evening, except for some jetstream-level moisture remaining (illustrated below for UTC 06:00, after midnight) that may appear as high cirrus, and low-level clouds or fog patches that may form (from moisture from sublimating snow) in regions where winds remain light during the evening, and before windspeeds increase ahead of a cold front before morning.

Will skies be clear Monday evening over southern Ontario?

Clear skies are expected, except for southwestern regions after midnight, where high-level moisture will be spreading northward (illustrated below) from the southern US as well as low-level moisture that will probably cause cloudiness by Tuesday morning over southwestern Ontario. A noteworthy problem for sky observers could be fog development during the night, due to strong nocturnal inversions developing under the clear skies, and high humidity caused by snow sublimating during Monday afternoon under the sunshine.

Will skies be clear over southern Ontario Sunday evening?
It looks like skies will be at least partly clear after sunset before some mid-level moisture moves over southern Ontario (illustrated below) and causes some cloudiness. Also, the upper-level weather disturbance moving the moisture across southern Ontario may cause occasional overcast skies with snowflurries.

Will skies be clear Thursday night over southern Ontario?

Mostly clear skies are expected, except for some high-level moisture remaining over southern Ontario (mostly moving eastward from southern Ontario with the jetstream during the afternoon) and some low-level moisture (illustrated below) that may cause some clouds to be visible in the bright moonlight.

Will skies be clear over southern Ontario Wednesday evening?

It looks like skies will be mostly cloudy, due to mid- and high-level moisture spreading northward over southern Ontario (illustrated below) from a nearby jetstream, but breaks in the cloud may allow the bright moonlight to occasionally give the appearance of partly or mostly clear skies.

Will skies be clear Monday night over southern Ontario?

Clear skies are forecast, at least until early morning (earlier in SW regions) when high-level moisture will be starting to spread northeastward across southern Ontario ahead of Tuesday’s warm front.