Like clockwork, the rain fell right on schedule. Gathering stormclouds had shaken off occasional droplets over the last three hours, but by 4:00 the thunderheads had reached full strength, and the teasing was over. With a furious, deafening boom that reverberated across the San Juan Mountains, the storm unleashed a torrent of rain upon the grasses and stones of the alpine tundra. Fortunately for me, by then I was sitting comfortably in my tent below treeline, reading a tattered, secondhand book of old ghost stories. For all their thunderous boasting and bluster, Colorado’s summer thunderstorms are shamefully predictable, if you pay attention to the signs.