As you probably have read in Gold's book, the underground temperature tends to be at the annual average for your area. Ane the deeper one goes, to a reasonable depth, the closer it is to that average, and the more constant it is. I would guess that you would be in pretty good shape there in Canada?
The other thing to do is to shade the ground around your house, with shrubs, trees, etc. Even grass is a good thing. Rocks, or something like an asphalt driveway, will conduct heat into the ground, and possibly into your cellar, if it is close to a basement wall. So, ideally, a passive cellar is best on the North side of the cellar, but not absolutely necessary, depending on what sort of summer sunshine and heat the South side is likely to get.
It should be easy to insulate an area in your basement for a good passive cellar. I haven't completed insulating a space in my cellar yet, but the 1st floor is air-conditioned and it is a forced air system with ductwork in the cellar which tends to cool off that area too when it runs. Then too, I have a large tree on the South side of the house that provides shade in the late morning and afternoon. Last year, in late August, when the underground temperatures tend to peak, the cellar got up to 68F at eye level, and only 64F at ground level. And I wasn't running the A/C very much, except during the late afternoon.
So wait till you move in and the locate a space that isn't near a source of "heat ingress", like a driveway, or large rocks outside, etc. You should be fine! ...Paul