Alright so my name is XXXXX XXXXX I have assisted other just answer customers like you with similar questions. Just keep in mind "best" is going to be a subjective answer. My answer will encompass a few things so you can get a really good idea.
Generally speaking San Diego in California is agreed upon as having the most consistent comfortable weather all year round, with comfortable temperatures and low, consistent dewpoints. As you probably already know dewpoint can make a profound impact on the feeling of being comfortable.
San Diego is usually around 70 degrees, give or take a handful, with a dewpoint of roughly
50-60F. The west coast is very comfortable for this reason, though there are a few places, because of the Pacific ocean's influence that don't really get "hot" per se for the summer, though still very warm.
The SE US is very warm and known to be quite humid. It is not uncommon for dewpoints to breach the 60-75F mark and other wise is no recommended if you are concerned with dewpoint.
As a very general statement, just to get an idea, anything west of Colorado is going to have a much lower mean dew point than that east of it.
Though really for weather as far as temperature, rainfall and dewpoint, San Diego is probably the most comfortable and consistent.
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