I tend to plant perennials, those that come up year after year, because they're the backbone of a "lazy garden," needing little work once they get going. However, a couple years ago, I noticed that in October and November many of the temporary plants, the annuals, were in full bloom and making a great show.
Yes, they turn. brown once there's a good frost, but some row cover, often sold for protecting vegetables, can keep the annuals going until December, perhaps. Our early frosts rarely last long and the row cover is easy to pull over and pull off.
To keep annuals blooming, cut off the spent flowers so they don't turn into seed pods or capsules. Setting seed is a signal to the plant to leave off flowering, put all energy into seeds. I do like to let the later flowers go this route, as a kindness to the plant you might say. And, there are some seeds worth saving and sowing myself next year.
The annual morning glory, 'Grandpa Ott's,' with Savoy cabbage