No, they're almost always gone by July 4th.
But the clouds of small and ever-hovering (around your eyes, nose and mouth face-flies) last until Winter rains. They don't bite, thankfully, though they're very pesky until you acclimate to them. They're worst in the oaks, when you're sweating profusely. If you haven't experienced this yet to know whether it will drive you completely bonkers, best bring a headnet and/or some kind of bug-prrof shelter that will allow you to escape them for a siesta in the heat of the day.
