It's going to be difficult to find the cool part of the day over the next week. I would recommend going as early as possible. The sunrise is 5:58am today, probably your most favorable conditions! It will be a touch less humid today with dewpoints in the 60s.
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The good news is that, each day, there's a bit less sunlight from day to day. The bad news is that it will still get hotter and hotter until late August.