The spring is a pleasant time to visit the park, with lower crowds and normally comfortable temperatures. The Virgin River is often too high for hiking the Narrows in spring.
The summer is the time of highest visitation, but is not the best time to visit. Temperatures can get very high during the day, and many of the exposed hikes can be uncomfortable or even dangerous. However, the Narrows hike is ideal in the heat of summer. Expect all lodging and camping to be full during the summer.
The fall is perhaps the best time to visit. Temperatures return to comfortable levels and the crowds thin. Lodging is more likely to be available, although camping can still fill at times.
The winter is cool but not often cold. Light snows in the canyon are occasional. The winter is the only time private vehicles are allowed on all park roads.