If it's a good year for blueberries, there should still be some during the first half of August... I know I've picked blueberries in the past at that time. The cool weather this year might have delayed the season so that the picking will be later and the extra rainfall that's been coming down is known to be good for blueberry production. And some spots are later than others.

There may have been a hard spring frost this year which could have killed off the blooms which could mean no berries.... I haven't been out to any blueberry spots yet but if you see blueberries growing somewhere, it's good sign  to search further and higher ground is usually better protected from frosts during spring, so a rocky blueberry barrens area up on a hill might be worth a look.