Just for the peach tree, because we’re hovering in the mid- to high-60s. A couple people on this forum have told me peaches won’t callus until they get to the low eighties, or at least they won’t callus quickly. We’ll see, I guess-- money already wasted! 
but thanks for the concern. At least if many of the grafts on my peach fail I have some scions left in the fridge and I can do a few over again, later when it’s warmer.