I got altitude sickness once, and I hope I never get it again. I’d left the Sierras on the Pacific Crest Trail to come home (Boston) to a family wedding. I hadn’t gotten sick when I’d been hiking the Sierras, as my body had adapted to the climbs. The problem was when I returned. I got off the plane and immediately took a prearranged ride straight up to Onion Valley Trailhead (9400 ft.) and from there, started climbing to Kearsarge Pass (11,760 ft.). Within minutes I experienced a slight headache and shortness of breath. Within twenty minutes I had no legs and a worsening headache.
For two days, I had to alternate a half hour of rest with a half hour of slow hiking. I felt lousy. I was weak, and most of the time my head felt as big as a basketball. I should have gotten a room that day I returned, and the next morning climbed half way and made camp. I won’t make the mistake again.
Hiking Tip: Acclimatize
Here’s a different example. Prior to starting the PCT at the Mexican border in early May, I had spent several days in sunny San Diego. I had come from Boston temperatures that were in the low 50’s, but now in the desert it would get into the 90’s. The days spent adapting to a warmer climate in San Diego served me well. At the PCT border trailhead, I met another hiker who had arrived from Michigan just the night before. He was lean and mean and young, but he was toast by afternoon. He’d made the mistake of not adapting to the climate. He slept okay that night and gamely poled off the next morning, but the sun and 90+ temps took him out again. I and two other hikers moved ahead, and that was the last we saw of him.
The CDT photo was taken somewhere in southern New Mexico on a typical hot day.