The South Rim is open all year, as are most visitor services there. Because it's so far from the nearest towns,
many people who work there also live there in the park, and Grand Canyon Village even has its own
school (K-12) with more than 300 students. Facilities at the North Rim are open only from mid-May until mid-October.
After that, when snow causes closure of the road to the North Rim, that road remains closed until mid-May.
Temperature at the bottom of the canyon averages about 20 degrees (F.) warmer than at the rim, year round. It is not unusual for the temperature at the river to be over 100 degrees in the summer. The South Rim typically gets 50-100 inches of snow in the winter; occasionally it snows at the river, too.
The following is a direct quote from the official web site of the National Park Service:
" WARNING: There are no easy trails into or out of the Grand Canyon! "
Visitors who decide to hike to the bottom of the canyon are discouraged from doing so if stormy weather is forecast, because of danger from lightning and flash floods. Attempting to hike down and back up again in one day is also strongly discouraged.
The rugged terrain obviously makes it a difficult and strenous hike, and fatigue becomes an even greater problem for anyone not accustomed to the thin air at high altitudes. It's recommended that hikers carry with them plenty of water and food (appropriate food for a rigorous hike), to stop frequently to rest, to take advantage of places along the trails that have available water, and to camp for one or even two nights before trying to complete the climb back to the South Rim. Minimum three nights camping in the canyon are recommended for a hike from the North Rim to the bottom and back to the North Rim, or for a rim-to-rim hike across the entire width of the canyon. A Backcountry Permit is required for overnights below the rims.
Some serious hikers (and perhaps also some uninformed and/or delusional inexperienced hikers) don't pay attention to the recommended times to allow for hikes into the canyon. Some make the round trip from rim to river and back to the rim again, all in the same day. Some experienced hikers even traverse the entire width of the canyon, from one rim to the other, in a single day -- nearly 25 miles of hiking in very rugged terrain, including an ascent of a mile or so up the canyon wall!
In a league of their own, extreme hikers have made the 45-50 mile round trip from one rim to the other, and then back again to "point A", with no overnight stop, the goal being to complete that trip in under 24 hours. Some have successfully done that, and some who succeeded continue to challenge themselves by returning again and again, trying to better their previous best time! I have read several journals on the web that were written by those extreme hikers. Accounts of their hikes across the canyon sound much more like torture than fun to me!
Just the thought that there were people actually climbing around in the canyon while I was there tired me out. After a relaxing train ride back to Williams, I camped out on a comfortable bed in a motel room before getting into the car the next morning and heading out toward Oak Creek Canyon and Sedona.