Spring (March–May) is the best time to visit. Days are warm and clear, the trails are passable, wildflowers bloom on the rim, and the crowds — while building — have not yet reached summer levels. Temperatures below the rim are comfortable for hiking in April and early May before the heat sets in.
Summer (June–August) brings the peak crowds and dangerous heat. The South Rim sits at 2,100 metres (6,900 ft), so rim temperatures are pleasant — 20–27°C — but the inner canyon regularly exceeds 40°C at river level. Hiking below the rim in summer is dangerous without very early starts and large quantities of water. The North Rim is open from mid-May through mid-October and is cooler and much less crowded. Afternoon thunderstorms are common in July and August.
Autumn (September–October) rivals spring as the best time to visit. The summer crowds have thinned, temperatures are cooling, and the canyon light in October is exceptional. Below-rim hiking becomes safe again in September as temperatures moderate.
Winter (November–February) brings snow to the rim and a dramatic drop in visitors. The South Rim stays open year-round, though some facilities close. The canyon walls dusted with snow are beautiful. The North Rim closes to vehicles from mid-October and is inaccessible in winter. Ranger programmes continue year-round.