TOD - You would think the coldest would be sometime when I lived in Michigan, but it actually was here in Middletown, OH, maybe at the same time DR John G remembers. January 10, 1982, the day the Cincinnati Bengals played the "Freezer Bowl," a game we were smart enough to watch on TV. Air temp was -9, with wind chills of -37. It was also pretty cold in Delafield, WI, when I went with Richard to his seminary in January of 2008.
Hottest, of course, was in Phoenix when we visited Mom several times during the summer. I don't remember exact temps, but I do remember that we had to wait until it cooled off in the evenings to go swimming. We actually were waiting until her pool was shaded so that our (then) blond little boy didn't burn to a crisp.
Most uncomfortable, though, was New Orleans in late June when I was there for the 1993 ALA Annual Conference. I thought I was tough after a couple of Phoenix summers, but adding the humidity to the high temps made me think I was going to die.