No later than which week in October should autumn foliage be seen, in Ontario?
score:4
Accepted answer
You can check fall colours on websites that show maps or give text reports:
https://www.ontariotravel.net/publications/fallcolourreport.pdf is text only, updated once a week. Currently says "Many long-time Algonquin Park
fall colour watchers are predicting the peak Sugar Maple colour to be later than the September 27 average of the past 40 years."
http://ontarioparks.com/fallcolour is supposed to have a map according to other people's screen shots, but it doesn't work for me. It has text for sure.
I like to do my leaf peeping Thanksgiving weekend which would be Oct 10/11/12 this year. I suggest picking a weekend and then you just vary how far north you go.