The Grand Canyon's South Rim is a great summer destination. Located in Northern Arizona, the Rim sits 7,000 feet above sea level, which makes for comfortable daytime temperatures. It's the inner gorge where you need to take precautions against the heat.
May through September are the Canyon's summer months. May, the coolest month, averages 70 degrees during the day and 39 at night. July, the hottest month, reaches a high of 84 degrees and a low of 54.
The rim-top climate is ideal for exploring the Park's key lookouts, including Mather Point, Yaki Point, Yavapai Observation Center, Hermit's Rest, and more. It's also a great time to pitch a tent at Mather Campground.
The Park also offers a network of trails that go "below the rim." Two of the most popular are Bright Angel Trail and South Kaibab Trail, which switchback to the bottom until they reach the Colorado River.
If you take one of these trails, know this: The Inner Gorge is up to 20-plus-degrees hotter than the top. For example, in July, when it's 84 degrees in Grand Canyon Village, it's 106 degrees at Phantom Ranch, a lodging area at the bottom.
If you hike into the canyon, follow these recommendations:
1. Bring water. Lots of it. If you are in the Canyon in the middle of the day, your body may require up to a gallon of water an hour. Hydration packs are recommended.
2. Hike / walk in the early morning or late evenings . It's relatively cooler at these times. Plan your walk back during cooler times as well.
3. Bring salty foods . It sounds counter-intuitive, but as you perspire, you lose salts. Many people swear by salty trail mix and bottled water.
4. Dress for heat . Loose fitting clothing (dry-wicking material works great). Full-brimmed hats. Boots and running shoes are advised. Stay away from flip-flops.
5. Sunscreen . Up to SPF 50. Use it often. The sun's rays are strong.
Do not hike to the River and back to the Rim in a day. The distance is deceptive. It's nearly a 5,000-foot vertical drop to the bottom. Hiking up that in 106-degree weather has resulted in heatstroke for many uninformed hikers (heatstroke is a condition when the body is unable to produce enough sweat to cool itself).
Rainfall on the South Rim is minimal. However, there is a "sub-season" called the Monsoon, which goes from July to August. It's characterized by thunderstorms and torrential downpours: One second it's raining buckets and the next it's sunny. In the Gorge, there are flash floods; your best defense is to seek higher ground or not hike the smaller bottom-lying Canyons during storms.
Temperatures are temperate at the top, making exploration comfortable and enjoyable. Inside the Gorge, temperatures spike, especially in July, when the difference between top and bottom is 20-plus degrees. Take a few simple precautions and a Grand Canyon tour can be the trip of a lifetime. Just remember: What goes down must come up. If you prefer to remain at the top, take a stroll on the Rim Trail, a flat, paved trail that gently follows the Canyon's edge. In addition, bring plenty of water, dress appropriately, and walk during early morning and later afternoon. Following these simple guidelines will ensure that you have a safe and pleasurable South Rim trip.