I just finished dropping off my second to last flowers of 2016. Since I grow everything myself, the flower delivery season ends just a little after summer does.
Most people are thinking about mums and asters in late September and early October, but they aren't the only flowers that love the cooler weather. Dahlias, zinnia, cosmos - every season I'm surprised at how they rally after a sweltering August. Some, like the anemone pictured above, don't even bloom until late September or early October.
If you leave a little room in your garden beds, you can sew seeds (in zone 6) for cosmos, zinnia, and other cutting annuals every two weeks from early May through late June for a continual display of flowers. Or, if you'd rather seed it and leave it, plant your flowers once and be sure to remove spent blooms to encourage your plants to flower continually all season long.