California is so large and so diverse that depending on where you want to visit most any time would be a good time. The beaches are great nearly year round, the mountains have snow and skiing in the winter months and the rest of the time are just beautiful. The wine country area is beautiful most year round. Farther north the weather and scenery is beautiful in their own right. Then we have the big trees - the sequoias, which are best except for perhaps Dec - Feb. South is beautiful year round even the desert areas. I guess every time is a good time to visit - except for the traffic! LOL