Late-afternoon cloud cover builds with predictable regularity across the desert, accompanied by swirling winds and darkening skies before the downpour begins.
While some storms bring only light rain, an August deluge hit a remote stretch of the North Rim of the Grand Canyon with extreme force. Far beneath the rim, scores of trekkers were pitching tents along Bright Angel Creek, looking up at the sheer rock faces they were scheduled to climb on their return journey.
