When the danger of frost has passed in your climate, it's possible to direct seed several tender summer annual "flowers" that will put on a magnificent show this year in the garden.
Try zinnias, sunflowers, marigolds, sorghum and millet. I find that the bigger the seed, the easier it is to track small seedlings in the garden, and these five all have large seeds.
If you're feeling like you can take on the challenge of smaller seeds, amaranth can be direct seeded this time of year as well, along with orach, chinese forget-me-not, coreopsis, and cress. I think of this group as "weedy" flowers, which in my mind means that they germinate easily and outcompete other seedlings in the field.
If it's still a week or two until frost is over in your area, you could always seed cosmos too; while tender when they are fully mature, cosmos can take light frost as seedlings. Likewise, calendula, borage and bachelor's button still germinate well this time of year, even though they can be seeded much earlier than this. Again, these yummy edible flowers are kind of like weeds and can flower well across a broad range of temperatures.