Before you wrote that, I'd been trying to figure out why the Fahrenheit scale is the way it is--what's so special about the number 32? Is there something even more special about 0? (I think it has to do with brine, or something.) Anyway, I'd thought about pointing out how that's all a bit iroquoisy, but it happens so often now that I think I'm just going to reserve that word for times when things are double-iroquoisy or lead back to Kateri Tekakwitha.
I imagine that elevation above sea-level might have a substantial impact on the boiling temperature of bagels as well. For the same reason that making a decent cup of tea on Mount Everest is well-nigh impossible.
You might think this is due to Boyle's Law. You would be only tangentially correct.