One of the few pleasures of advancing age is that, no matter how awful some looming catastrophe may be, you can always remember a time that was worse. On hearing the polar vortex was headed for Chicago last week, my wife and I smugly reminisced about having survived the coldest night in the city’s history — 20 January 1985 — when the mercury fell to -27ºF, or -33ºC. (Temperature scales are a nuisance in accounts of this sort — more on that below.) Spurning the temptation to huddle beneath blankets, we went out for deep-dish pizza, thinking we’d have the joint to ourselves. On the contrary, it was packed. We had to stand in line, mercifully in the unheated vestibule rather than the sidewalk. We had a blast. ‘Let’s see if they can top that,’ I said to my wife this time around.