In one day, a hiker can travel from the cold fir and aspen forests of the North Rim to the hot cactus country of the Canyon bottom—a climate change equal to that between Canada and Mexico. As on a mountainside, temperatures change with elevation, but with added canyon peculiarities. In winter, the sun's low angle allows only a few hours of sunlight a day to reach the Inner Gorge, creating a cooling effect. The situation reverses during the summer, when the sun's high angle turns the Canyon into an oven. At night, temperatures often drop lower than you'd expect, when cold, dense air on the rims pours over the edge into the depths.
In the Inner Gorge (elev. 2,480 feet at Phantom Ranch), summer temperatures soar, with average highs over 100°F; the thermometer commonly tops 115° in early July. Spring and autumn offer pleasantly warm weather and are the best times to visit. Winter down by the river can be fine too; even in January, days warm up to the 50s or low 60s and it rarely freezes. Only 9.4 inches of precipitation makes it to the bottom in an average year; snow and rain often evaporate completely while falling through the mile of warm Canyon air.
The South Rim enjoys pleasant weather most of the year. Summer highs reach the mid-80s, cooling during winter to highs in the upper 30s and lower 40s. Winter campers need warm sleeping bags to combat frosty nights when temperatures plunge into the teens. Yearly precipitation at the South Rim's Grand Canyon Village (elev. 6,950 feet) is 14.4 inches, with snow accumulations seldom exceeding 2 feet.
Although averaging only 1,500 feet higher, the North Rim in the Bright Angel Point area really gets socked in by winter storms. Snow piles up to depths of 6-10 feet in an average season, and the National Park Service doesn't even try to keep the roads open there from early November to mid-May. Summers can be a joy in the cool, fresh air; highs then run in the 60s and 70s. Bright Angel Ranger Station (elev. 8,400 feet) on the North Rim receives 25.6 inches of annual precipitation.
Most moisture falls during the winter and late summer (mid-July to mid-September). Summer rains often arrive in spectacular afternoon thunderstorms, soaking one spot in the Canyon and leaving another bone dry only a short distance away. The storms put on a great show from the rim viewpoints, but you should take cover if lightning gets close (less than seven seconds between the flash and the thunder) and especially if the hair on your head stands on end or if you smell ozone. As in mountain areas, the Grand Canyon's weather can change rapidly. Always carry water and raingear when heading down a trail.
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