Originally Posted by ridefar

It seems a mixture of random and programmatic to me. Random in the sense that certain airports are more likely (LAS weighed mine on check-in; the only time I have ever had this happen). And then periodically there are checks across all major Canadian airports at more or less the same time. Usually a prominently displayed SE tags means they don't ask during those. At least they never have for me. Bottom line is you *should* be OK, but it is not guaranteed.