If you're mainly wanting to sightsee, you will be staying at the rim, either South Rim or North Rim. The North Rim is closed from early November through May 15, but the South Rim is open year round. Summer is the best time of year to sightsee at the Canyon. High temperatures are often in the 80s, and afternoon rain showers in July, August and September cool things down beautifully and create dramatic skies and views over the Canyon's sheer depths. Winter months can be cold, windy, and snowy on the rims, so if sightseeing is your main interest, avoid winter months. Spring and fall are often beautiful times to sightsee but it can still be cold with late or early snow storms, wind...etc.