This thread has certainly wandered!
On the above.........we have had shorter transitions than usual, particularly in the GTA the last 2-3 years.
That, I think, is anomalous.
The urban heat island effect does affect Toronto weather such that we get warmer sooner than many other places in Ontario.
It isn't a dramatic difference in day time temps, when one compares to areas say 1/2 way to Barrie. Maybe 1-2.5 degrees C
But there is a more marked difference in night-time temps as dark pavement radiates heat at night, as do many building materials.
The difference at night is up to 4 degrees C.
That matters not just at night, but in the early morning temperatures as well.
You also get some other incidental effects which change your perception of season length.
For instance, trees will change colours more readily when day and nightime temperatures diverge more.
So when nighttime temps stay high later into the season, you tend to get late fall colours. Because the leaf is only sustained overall by daylight levels, the period of colour change is shorter with the warmth created by the Urban Heat Island, as the leaf's die-off date is largely unchanged.
This reinforces a perception of a shorter fall season.
At the same time, it makes for a hotter, less bearable summer at peak; with lesser but tangible effect of a warmer winter, also muting the perception of seasonal-shift.
In Europe there is wide variably in seasonal perception from North to South.
Like here, there is also a variation between larger cities vs smaller towns surrounded by farms or wild areas.
Southern Italy doesn't get much of a winter; while Norway's summers are rather short.