The balmy air at the North Rim was speaking to me. I should have been listening. Late September in these rarefied parts is normally brisk, sometimes even cold. On this day of our arrival we were comfortable in short sleeves. If it were warm here, the inner furnace of the canyon would be even hotter than normal. But the Nankoweap Trail was already playing with my head. I'd heard and read so much about its steepness, ruggedness, and dizzying heights I didn't even bother to think of its exposure to heat and sun. But in the end it's the heat that always matters in Grand Canyon. Always.