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This article on TripSavvy tells you how to track and predict fall colours all over Canada. For Nova Scotia, they say:
The Nova Scotia tourism website doesn't provide fall color reports, but there are other ways to track where the leaves are changing in the province. Follow @VisitNovaScotia on Instagram and @VisitNoviaScotia on Twitter. You can also search for #nsleafwatch on Instagram and Twitter. For a sure bet on seeing colors, visit Cape Breton Island during its Celtic Colours International Festival. You'll see fall colors along Nova Scotia's rugged coastline, in the mountains of the Highlands, and on the Cabot Trail.
You will have to choose among the following strategies:
Since every year is different it is impossible to know what will be the peak day this year. However, you should be able to choose a darn good day, especially if you're willing to be flexible about where you go once you reach the province. Since the "Fall Colours" event mentioned above is from Oct 5th to 13th, it seems like going for the 9th through the 11th should be a safe bet, and allow avoiding the weekend crowds.