At about five o’clock, it had cooled off enough that I was willing to go out for a long walk. I walked out of my sister’s air-conditioned house in Acton, Mass., into the heat. At least it wasn’t unbearably humid; it was merely mildly humid and oppressively hot. When I got off the main road onto a side street, away from car exhaust fumes, I could smell the warm earth, the roadside plants and weeds, the occasional tang of pollen. I passed a hay field that had just been mowed, with all the cut hay raked into rows so the baler could scoop them up, and the sweet smell of fresh-cut hay overwhelmed all the other smells. Then I got back onto a main road again, and once again the hot summer smells were lost under the exhaust fumes. That evening, Dad said his digital thermometer had recorded a high temperature of 99.9 degrees Fahrenheit.