Plant Hardiness Zone Map
Plant hardiness zones provide guidelines for what plants can grow where. Certain areas within a zone may have different microclimates depending on a number of factors such as topography and exposure to wind and sun. You may be able to create a small microclimate in your garden with mulch, walls, and other protections. "Pushing the limit" is quite possible.
Please ensure the plants you order are suitable for your hardiness zone and microclimate.
Plant Maps
Plant Maps offers an excellent interactive map of plant hardiness in Ontario.
Natural Resources Canada
Natural Resources Canada has produced plant hardiness zone maps since the 1960s. Their interactive map is a bit clunky, but their static maps are excellent.