My wife and I usually go in August or sept. May and after are less crowded because of the cold nights. Middle of summer is too crowded and kinda hot.
The ideal time to visit sequoia will be from April to October but if dont have a camp site reserved for yourself I ll suggest you should go in the first week of November, it starts getting cold but still is really good and not so much of rush so you can easily find a camping site.
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