The spring starts off cold and snowy at the higher elevations. Snows may be found on the roads at any time, sometimes closing them for short periods. The real visitation season in the parks starts around Memorial Day, when most services go into full swing.
The summer is the season of highest visitation. The higher elevations are usually pleasant, but the lower elevations in the foothills and canyons can get quite hot. The campgrounds in the Giant Forest area and all lodging are usually full. However, neither of the parks ever feels overly crowded.
The fall is a great time to visit. Crowds disappear after Labor Day and temperatures remain comfortable through October. Things turn cold and possibly snowy at the higher elevations in November.
The winter is quiet and often beautiful time to visit. Temperatures are low and snow is common in the sequoia groves. Roads are plowed and kept open except for short periods during or after major snowfalls.