Here in Ontario, the hard wood tree leaves don't start to change color and drop off until the over night temperatures drop to near zero C. That won't happen until well into October.
Cities and towns here prohibit the burning of tree leaves by residents. Instead the fallen leaves are gathered up and placed in big brown paper bags, which are collected by the municipal trucks and taken to open fields where they are turned into compost over the course of the winter. In the spring, the composted materials are dumped in local parks, and the residents bring containers and take the compost to use on their gardens at home. A much better way, compared to the old practice of burning leaves. JIM.