there's something special about -35C

there's something special about -35C, it's temperature limit for the flower buds on some plums and cherries. We usually get a dozen nights this cold in any winter, or I guess mornings because it's right before sunrise. I try to monitor them because it helps to know what cold exposure was on all of the fruit trees we're growing, this is the main test for zone 3 hardiness. we'll get some -40 but its usually a brief dip just a few times, I suspect exposure is temperature x time, but probably just being optimistic about the sweet cherries grafted in the laneway, or the european plums in their second winter grafted high up onto chokecherry, I want these to survive but nature doesn't care about what you want ;)