One thing. "Longer growing season" is not predicated upon temperature. Length of the day, sunlight, is a hard requirement for some plants. And the further north you go, the less the sun gets up over rhe horizon, even at noon.

So extending the time before frost, won't help many plants reach maturity. The days will be shorter, and when the sun comes up there is barely any light anyhow. Raw "daylight hours" are meaningless here, when the sun only gets barely over the norizon.

One month of June light is like 6 months of December light in much of Canada.